Journal of Research of the National Bureau of Standards Vol. 55, No.5, November 1955 Research Paper 2626 Properties of Piezoelectric Ceramics in the Solid-Solution Series Lead Titanate-Lead Zirconate-Lead Oxide:
Tin Oxide and Lead Titanate-Lead Hafnate 1 B. Iaffe/ R. S. Roth, and S. Marzullo
Compositional proximity to a morphotropic transformation between two ferroelectric solid-solution phases seems to yield ceramic transducers having desirable properties over a wide range of temperature. Examples of t his phenomenon were observed in the systems PbTi03-PbZr03, PbTi03-PbO:Sn02, PbTi03-PbZr03-PbO:SnO" and PbTi03-PbHf03. The dielectric and piezoelectric properties of ceramics having compositions in these systems and in t he system PbZr03-PbO:Sn02 are described. The composition Pb(Ti .. 5Zr .5,) 0 3 exhibits a high radial coupling coefficient, greater than 0.3, for temperatures as high as 275 0 C and has t he highest g31 constant, 1l.7 X 10- 3 volt -meters per ne\\·toll. For the series of compositions containing 30 percent PbO:SnO, in the ternary system PbTi03-PbZr03-PbO:Sn02 the tetragonal composition nearest the morphotropic boundary has the highest d31 value, 74 X 10- 12 coulombs per newton. The rhombohedral composition nearest. the morphotropic boundary sho\\'s the least change of frequency co nstant with temperature, a 2 perce nt variation over t he range of 25 0 to 225 0 C.
1. Introduction type structure, AB03, in which th e A ions occupy the corners and the B ions occupy the center position Piezo el ectric ceramic transducers can be fabricated of the unit cell, with the oxygen ions at the center of in a wide variety of shapes and siz es. Like other the faces. The ferroelectric compounds have been ceramics fired to hi gh temperatures, they are gener found to have either rhombohedral, tetragonal, or ally nonreaetive at ordinary temperatures. In COl1- orthorhombic symmetry. It is being recognized Lrast, crystal transducers must be formed by lapidary that studies of solid-solution series between known techniques from nearly-perfect single crystals. Many ferro electrics and other materials related in stru cture of the commonly-used ones are water-soluble; others can yield ceramic transducer materials of promise. dehydra te easily when heated. It is known that the piezoelectric properties and It is desirable to find ceramic composition s which the dielectric constant of ferroelectric barium titan ate are suitable for use as cIectromechanical transducers are enhanced at temperatures near those of poly over a wide temperature in terval. To produce such morphic inversions below the Curie temperature, a piezoelectric ceramic, it is necessary that the crys such as near 0° C [2]. At these inversion tempera tal structure of the material be devoid of a center of tures, the crystal form changes from one ferroelecLric symmetry. However, it must also be possible to modification of the perovskite structure to another. orient permanently the crystallographic directions 110m rece ntly, compositional boundaries have been of tbe component grains by an externally applied noted between ferroelectric phases of slightly d iffer field. ing structure [3] . An abrupt change in the structure The prevailing opinion indicates that piezoelectric of a solid solution wiLli variation in composition is ceramics can be made only from ferroelectric crys known as a morpho tropic transformation. These talline materials. These are regarded as ones having morpho tropic transformations [4] occur because of a crystal structure which contains a dipole mobile free energy differences between two or more alternate enough to orient itself parallel to jts neighbors in ad crystallographic modifications of a given basic struc jacent unit cells, and to be reversible by an applied ture type. As one ion replaces another in a solid electric field [1 ].3 solution, the energies of the different structures In polycrystalline form, the ferroelectric com change, and the crystal assumes the structure having pounds clifl'er in their ability to acquire and reLain a the minimum free energy. piezoelectric effect, even though each would show One example of morpho tropism between ferro strong piezoelectricity if a singlc-domai n crys tal of it electric phases in solid soluLion is found in the were tes ted. Barium titanate, widel.\" used as a system PbZr03-PbTi03 [3, 5] . In this system it ceramic transducer, is an example of a ceramic capa was found that the cia ratio of tetragonal PbTi03, ble of retaining a strong piezoelectric effect. ::vlost was decreased as PbZr03 was added in solid solution of Lhe other ferroelectric compounds, in ceramic form, until a morpho tropic phase boundary occurred at 55 are inferior. Although there is a steady j ncrease, the mole percent PbZr03. Solid solut ions higher in number of such known oxide type ferroelectric crys PbZr03 content were rhombohedral. Subsequen t t.alli ne compounds is small. Most of these com experiments by the present investigators [6 , 7] pounds are known Lo have a distorted perovskite showed that the room temperature dielectric con s tant and induced piezoelectric effects of ceramics I The work cO\'crcd by this report was sponsored b y the Offi ce of Ordnance Re· sf'arch, Department of the Arm~T. wiLh compositions in this system were enhanced as 2 Present addrcss, 'rhe Brush Laboratories Co. , Clevcland, Ohio. 3 Figures in brackcts indicate the literature refe rences at the end of this paper. the composition approached the phase boundary. 239 From a piezoelectric and dielectric standpoint, it controlled by firing the specimens in an atmosphere would appear that compositional proximity to a that contains lead oxide vapor. For this, the speci morpho tropic transformation is even more desirable mens were placed in a large (75 ml) platinum cruci than temperature proximity to a polymorphic trans cible, and separated from one another by platinum formation. In consequence, experiments were con foil , as shown in figure 2. A pellet of PbO+ Zr02, tinued on other solid-solution systems in which mor enriched in PbO over the 1: 1 molar ratio by 4 weigh t photropic transformations might be found. percent, was placed on top of the stack of specimens. This pellet provided an " atmosphere" enriched in 2 . Experimental Procedure PbO vapor to retard evaporation of PbO from the specimens. A smaller crucible was inverted over 2.1. Preparation of Specimens the stack of specimens and another " atmosphere" The materials used for these investigations in pellet was placed on top of it. The large, or outer cluded reagent-grade PbO, a high-purity hydrated crucible, was then covered. It was found to be possi Sn02, a commercially-pure grade of ZrO;, and a good ble, by varying the weights of these " atmosphere" commercial dielectric grade of TiO ~ . The Hf02 con pellets, to cause the specimens to lose weight, remain tained about 0.7 percent by weight of Fe20 3. It also unchanged, or gain weight. This procedure follows contained 3.1 weight percent of Ti02, for which al that of Shelton et al. [9] who used it to produce lead lowance was made in computing the batches. containing ceramic dielectric specimens. For the Batches intended to yield 25 g of calcined material heat treatment, a uniform heating rate of 4}6° C/min were weighed and ball-milled with distilled water was maintained up to the soaking temperature. After for intimate mixing. They were then dried under soaking the specimen for 20 to 60 min., the furnace infrared, mixed again in a mortar and, in most was allowed to cool naturally. Since the furnace is instances, pressed loosely into a pellet and calcined not massive, the initial cooling was quite rapid. at 800 0 C for % lu' in a covered platinum crucible. In general, the weight change of a specimen was The calcined pellet was ground thoroughly, and speci less than 2 percent. Specimens with less than 0.1 mens were then pressed at 15,000 Ib/in.2 in the form percent absorption were considered to be matured. of }~ - in. disks of 0.050 to 0.100 in. thiclL A few drops All specimens which were thought to have lost too of distilled water were added to prepare the powder much PbO, or were not well matured, were rejected. for pressing; organic binders were avoided. Com Absorption was measured by placing the weighed positions which were prepared in the ternary system specimens into a flask, evacuating the air in the flask PbZr03-PbTi03-PbO:Sn02 are shown as open circles by means of an aspirator, and then allowing CC14 to in figure l. enter the flask and cover the specimens. The speci The specimens were weighed dry, and heat-treated mens remained in the CC14 for about 3 min. Carbon in a platimum-wound resistance furnace. As Rob tetrachloride was selected for this procedure since it erts [8] pointed out, the lead oxide in lead zirconate allowed a rapid method of measurement. The re and its solid-solutions is volatile. Its loss can be sults were then computed in terms of equivalent PbO:SnO 'water absorption. z In addition to the absorption, the linear slu'inkage and the apparent density were measured as indica tions of maturity. The linear shrinkage was ob tained by comparing the diameter of the disk-shaped specimens before and after heat treatment. The apparent density was obtained by calculation from the diameter and thickness of the specimens and their fired weight. The values, because of slight warping and eccentricity, are accurate to about 2 percent and are suitable for comparison purposes. The values of heat treatment and ceramic properties of the com positions studies are listed in table 1. As desired, X-ray diffraction patterns were ob tained with a Geiger-counter type X-ray diffrac tometer using CUKa radiation. These tests were generally made on intact ceramic specimens, al though, in a few instances when orientation difficul ties were suspected, powder samples were used . However, it was preferred to use specimens intact so that the same specimen would serve for other tests. From the lattice parameters, and the molecu MOLE BASIS lar weight of the solid solution based on its nominal F I GURE 1. Com positions studied i,n the ternm'Y system PbTi0 3- PbZr 0 3-PbO:Sn02 and the morphottopic boundaTies at 25° C composition, the theoretical density was computed. for part of this system. After the X-ray measurements, silver pas te was The region near PbO:SnO, is characterized by dissociation. F,·ferroelectric, applied to the disk faces and then fired on to form tetragonal; F,-ferroelectric, rhombohedral; A,-antiferroelectric; O-compositions studies. electrodes . 240 - ~ ______- ----~ - --- -J
TABLE 1. Batch composition, heat treatment and ceramic pro perties of designated solid solutions
Uotch co mposition H eat treatmen t Equiv. Theoret· N umber I alent Apparent water Shrinkage density ical PbZrO, PbTiO, I PbO:SnO, PblIfO, Temperature 'rime absorption density I I ------mole % mole % mole % mole % o C min % % kq/m' kq/m' 1 30 70 _.. ------1220 30 0. 02 19 7.3 8.0 2 40 130 ------0 1220 30 . 00 17 7.3 8.0 3 50 50 -- .-. --- - 1220 30 .00 15 7.1 8.0 4 52.5 47.5 ------1220 30 . 00 15 7.2 8.0 5 55 45 ------1220 30 . 00 15 7.2 8. 0 6 57.5 42.5 ------1220 30 . 00 14 7.2 8.0 7 60 40 ------.. --- - 1220 30 . 00 14 7.3 8.0 8 70 30 -- ---_._-- - 1220 30 . 00 14 7.5 8.0 9 80 20 ------· 1220 30 . 00 13 7.4 8.0 10 90 10 --.------·1220 30 .00 13 7.2 8.0 11 -- -- - 75 25 ------\l00 130 . 00 19 7.7 8.3 12 --- .... 55 45 -- --- 1175 30 . 00 16 7.9 8. 7 13 ------50 50 -- - 1150 30 . 03 16 8.0 8.7 14 ------47.5 52.5 ------.. 1150 30 . 02 17 8.2 8.7 15 ------45 55 -. -. ---- 1150 30 . 03 17 8.0 8.7 16 --. ---- 40 130 -----.-- 1150 30 . 06 18 8.2 8.8 17 --- - - 35 65 ------1150 30 . 09 17 7. 6 8.9 18 --- - - 25 75 ------. - 1100 130 . 00 22 7.6 9.0 19 90 ------10 ---- 1225 60 . 14 13 7. 4 8.2 20 80 --- 20 ------1210 30 . 05 1l 7.4 8.3 2t 70 --- 30 -- -- - 1250 20 . 41 14 7.5 8.5 22 50 --- 50 ------1300 130 . 00 19 7.9 8.7 23 30 --- 70 -- ---. - 1225 130 .20 2t 7.8 8.9 24 18 72 10 ------1230 30 .00 13 7.3 8.2 25 36 54 10 ------1250 30 . 03 13 7. 0 8. 1 26 38. 25 51. 75 10 ------1250 30 . Ot 14 7.2 8. 2 27 40.5 49.5 10 ------1250 30 . 00 14 7.2 8.2 28 42.75 47.25 10 -- ---. 1250 30 . 04 14 7.6 8.2 29 45 45 10 ------1250 30 . 00 14 7.6 8.1 30 54 36 10 ----. 1250 30 . 02 13 7.6 8.2 31 72 18 10 -- -- 1250 30 . 00 t4 7.5 8.1 32 16 64 20 ------1230 30 . 00 14 7.5 8.3 33 24 56 20 -- --- 1250 30 . 01 14 7.5 8.3 34 32 48 20 -. ----- 1250 30 .00 1:1 7. 7 8.3 35 34 46 20 ------. 1250 30 . 00 13 7.7 8.3 36 36 44 20 ------1250 30 . 00 14 7.7 8.3 37 38 42 20 ------1250 30 . 01 14 7.8 8.3 38 48 32 20 ------1250 30 . 00 14 7.9 8. 2 39 64 16 20 ------1270 30 .03 15 7.6 8.3 40 14 56 30 ---- 1250 30 .02 14 7. 6 8.5 41 22.75 47.25 30 ------1250 30 . Ot 15 7. 8 8.3 42 24.5 45. 5 30 ------1250 30 . 00 14 7.8 8.5 43 26. 25 43. 75 30 ------1250 00 . 00 15 7.8 8.4 44. 28 42 30 - . ------1250 ao . 00 14 7.8 8.4 45 42 28 30 ------1250 00 . 01 14 7.8 8.4. 46 52.5 17.5 30 ------1250 00 . 06 14 7.6 8.4. 47 56 14 30 - 1275 30 . 04 13 7.6 8. 4. 48 59.5 10.5 30 ------1250 20 . 31 13 7.6 8.4. 49 63 7 00 ------1250 20 . 42 13 7.5 8. 4. 50 66.5 3.5 30 ------1250 20 . 14 14 7.7 8.5
51 6 54 40 - - --- 1250/1225/1200 b 60-60-60 . 40 15 7.2 8.6 52 12 48 40 ---- 1250/1225/1200 b 60-60-130 . 09 14 7.6 8.6 53 13.5 46.5 40 -- 1250/1225/1200 b 60-60-130 . 05 14 7.6 8.6 54 15 45 40 -- 1240/1225 b 60-60 . 11 14 7.8 8.6 55 16. 5 43. 5 40 ----- 1240/1225 b 60-130 . 03 14 7.8 8.6 56 18 42 40 - --_. 1240/1225 b 60-130 .07 15 7.8 8.6 57 30 30 40 ------1250 30 . 05 15 7.9 8.6 58 48 12 40 ---- . --. 1240 130 . 03 15 7. 9 8.5 59 3.75 46.25 50 ------1125 30 1. 04 13 7.6 8.3 130 5 45 50 ------1125 30 0. 97 14 7.6 8.3 61 6.25 43. 75 50 ------1125 30 1. 01 14 7.6 8.2 62 7.50 42.5 50 --- _.--- 1125 30 0.94 14 7.7 8.3 63 8.75 41. 25 50 ------1125 30 1. 02 14 7. 7 8.3 64 10 40 50 ---- - 11130 30 0.82 14. 7.6 8.3 65 ------90 ------10 1250 30 2.8 8 6.6 8.3 66 --- -- 70 ------30 1300 130 1.3 8 7.4. 8. b 67 --- - 60 -.--- 40 1300 130 0. 00 8 8. 1 9.0 68 --- 55 -- 45 1300 60 . 00 9 8.a 9.1 69 -- - 52.5 - - 47. 5 1300 130 . 00 10 8.5 9.2 70 50 - - 50 1300 60 . 02 9 8.4 9.2 71 -- 47.25 52.5 1300 60 . 00 10 8.6 9.3 72 - 45 55 1300 60 . 01 lO 8.6 9.3 73 -- 42.5 57.5 1300 60 .02 9 8.7 9. 4 H 40 -- 60 1325/1300 b 60- 60 .03 8 8.4 9.5 75 --- 30 -- - - 70 1325/1300 b 130-60 . 09 8 8.3 9.7 76 --- - 10 - - --- 90 1325/1300 b 60-60 . 41 9 8.8 10.1 l • ot calcincd_ All others calcined at 800 0 C for 30 min. b Indicates repeated heat treatment of same sample.
I
241 r
2.2. Dielectric Measurements where kr=radial couping coeffieient ia= radial antiresonance frequency At least 24 hI' after the specimens were silvered, i T= radial resonance freqnency measurements were made of the dielectric constant and dissipation factor at 25 0 C, with less than The piezoelectric properties were evaluated further 40-percent relative humidity. The measurements for specimens having their composition close to were made at frequencies of 1 kc, 50 kc, 1 Mc! and one of the morpho tropic boundaries between ferro 20 Mc. The 1 kc measurement was made with a electric phases. :Measurements were made of the capacitance bridge; at the other. fr?quenci~s, a radial resonance and antiresonance frequencies and Q-meter was used .. ro s~ow the va~latlOn of dwlec of the 1 kc dielectric constants at a series of elevated tric constant and dissipatIOn factor with temperature, temperatures below the Curie point. From these, measurements were made from -500 C through the the frequency constant (the product of the disk Curie temperature, at a frequency of 1 Me. From radius and the radial resonance frequency) and the 0 - 50 C to 25° C a twin-T impedance measuring d31 and g 31 piezoelectric constants were computed, circuit was used on the specimens which were a,s well as the radial couping coefficient at each contained in a refrigerated cabinet maintained at the temperature. For this measurement, the specimen desired temperature. A Q-meter was u~ed for the was placed on a hot plate which was heated slowly temperature range fro.m 25° C t~ the. Cune ~empera through the desired temperature interval. Tempera ture, which was as hIgh as 420 C m one Instance. ture was measured with a chromel-alumel thermo- I The specimens were kept on a silver slab, the temper couple embedded in a control specimen next to the ature of which was raised approximately 4 0 C per one being tested. minute. As each desired temperature was reached, The coupling coefficient squared indicates the a measurement was made. Temperature was ability to transform electrical energy to mechanical measured by means of a chromel-alumel thermo energy, or, conversely, to transform mechanical couple imbedded in a control specimen resting next energy to electrica1. The d constant indicates the to the test specimen. These measurements were charge produced by a unit force or the deformation then plotted as a function of temperature. Any produced by a given potential. The g constant irregularities which might be found in such curves indicates the potential gradient (open circuit) caused I would be indicative of polymorphic transformations. by a given stress, or conversely, the strain produced by a given charge density. The first subscript 3 2.3. Polarization refers to an electrical field in the direction of polari zation. For a disk, this is usually paran el to the After dielectric measurements were completed, the direction of thickness. The second subscript 1 specimens were polarized by subjeeting them to refers to a strain normal to the polarization direction, strong d-c fi elds. The specimens were kept im alined with any disk radius. mersed in a dielectric medium of clean carbon At room temperature, in addition to the formula tetrachloride at room temperature. Generally, it noted for coupling coeffici ent, the following expres was desired to maintain a voltage gradient of 150 sions, adapted from Mason [10], were used: v/mil (or 150 kv/in. ) for 1 hr. For some composi tions this could not be done. Even though attempts were' made on several such specimens, excessive sparking or . electrical. leakage oecurre~. In these instances, pIezoelectnc data for less mtense fields were reported. where d31 = transverse piezoelectric constant, coulombs 2.4. Piezoelectric Measurements newton CT = Poisson's ratio, taken as 0.3 The chief figure of merit used to evaluate the Eo = permittivity of vacuum pie zoelectri~ properti~s of the .ceramic disks was the = 8.85X IO - 12 farads/meter radial coupmg coefficlCnt. ThiS was tested one week ET = relative dielectric constant at temperature after polarization by measuring the. resonance and T (25 ° C) and at a frequency below an antiresonance frequencies of the radIal fundamental resonances (1 kc). mode of vibration of a given specimen. A scheme newtons essentially similar to the one described by Mason Yff= elastic modulus, evaluated as [10, p. 292] was used, although the d-c bias shown meter2 was not employed. Frequency was measured. by follows: the dial calibration of a signal generator. When desired this was checked ,yith a calibrated frequency meter.' The fo llowing equation, adapted from Mason [10], was used: where a = disk radius, meters ~=251ia iT d 't kilograms l - k; . iT p= enS1 y, m eter 3 242 also no lower polymorphic phase tran formations, such as charactel'i7.e barium titanate. At room tempera ture, its tetragonal ela ratio is l.06, which represen Ls a relatively large distortion from the ideal cubic where g31 = transverse piezoelectric constant, perovskite structure. Lead titanate was known long meter volts befo re its interesting dielectric proper ties were newton realized [11, 12 , 13]. Given sufficient time, the To evaluate the ri3l and g31 con stants at the elevated compound forms completely at temperatures as low temperature, the following expressions were used: as 375 ° C [13 ]. Sillce PbTiOs is ferroelectric, oriented single crystals of it should display a s trong piezoelectric effect. However, in ceramic form, specimens of PbTi03 frequently break after cooling through the Curie temperature [14] . Experiments with solid where superscript A denotes room temperature and solutiolls rich in PbTi03 indicate that room-tempera superscript B refer s to the elevated temperature ture polarization by attainable d-c fields leaves no perceptible piezoelectric effeet, presumably because and the cia ratio is so large t bat reorientation of the domains would necessitate excessive deformations and stresses at the grain boundaries. Polarization at elevated temperatures near the Curie poin t would This meLhod takes changes in elasticiLy in Lo ac be difficul t because of condueLivity. count by means of the frequency raLio. It ignores ? nl y th ~ s m a~l variatio~ s in density anrl Lh e changes, b. PbZr03 if any, 111 POI sson 's ratio. At each of tb e elevated temperatures Lhe radial Although PbZrOs has been known for some Lime coupling coefficient and the frequency cO~1stant wcre [15], iLs unusual dielectric properties [16] were calculated separately from the measured values. noticed only a few years ago. L ead 7.irconaLe is considered to be antiferroelectl'ic, and thus will not 2.5. Choice of Reported Values form a piezoelectric ceramic [17 , 1 , 19]. ILs X-ray powder pattern, at fLrst approximation, is A series of heal, treaLmen Ls yielded specimens wi th Lhat of a tetragonal p crovskite with c/a< 1 [2 0]. varying absorpLion , fired density, and degree of It has ince been recognized [18] that, although Lhe m echan ical perfection. It was clear that maximum primitive cell does havc t his structure, the larger density and minimum aosorpLion yield ed the liighes L true unit cell is of orth orhombic symmetry with an valu?s, particularly of radial coupling coefficien t, anLiparallel arrangement of dipoles. This anLi provIded tbaL cracks or in clu sions were a bsenL. parallel shift causes tb e antifeIToelectric pl'oper Lies. The values reported for Lh e m easured properLics werc It also results in super sLrucL ure lines in the diffrac taken from an individual specimen Lhou gh t mosL tion pattern. nearly to approximate the ideal value of the proper There is a ferroelectric phase that is close in energy t ies of the m aterial under consid eraLion . For each to the antiferroelectric phase at temperatures just composition, 1 to 10 matured specimens were below the Curie point [17]. As a result, a plot of measured. For the compositions close to a morpho dieleetl·ic eonstant as a function of temperature t ropic phase boundary, a larger number of specimens resembles that of a typical ferroelectric. However, of each vvas tested. In those compositions where the dielectric hysteresis loops which typify a fe 1"1"o maturity was not attained, the values reported arc electric are absent. those for the specimens with the lowest absorption. Inasm.uch as no specimen was perfect in every c. PbO:Sn02 respect, lt was felt that the specimen wi th the highest There is some question about th e stability of a coupling coefficient would also have a dielectric perovskite-type 1:1 compound of PbO and n0 2, and constant that most nearly approached the ideal even about its existence. Coffeen [21] has reported valu e for the composition. Systematic variation of the properties of a lead stannate precipitated from composition indicated that choices of this kind were solution as the di-hydrate. ·When dehydrated, justified. this material has an X-ray pattern which we con sider to be that of a dis torted fluorite type structure. 3 . Results and Discussion It. seems possible t,hat t his phase, instead of AB03, may have the formula-type AB04 like other fluorites. 3 .1. Properties of Lead Components Naray-Szabo [22] reported a tetragonal perovskite structure differing from that of Coffeen's dehydrated Q . PbTiOa material. W e have not observed this perovskite. The fluorite-type phase sometimes appears as a Lead tiLanaLe is a ferroelectric perovskite, isomor diluent in perovskite-type solid solutions rich in phous wiLh barium titanate (tetragonal, cia> 1) [11 ]. PbO :Sn0 2. However, a sample of the fluorite-typE' Its Curie temperature is near 490° C, and there are material that was heated in air to 50° C was found 243
I ~ to be partially decomposed into free Sn02 and an TABLE 2. Lattice parameters of designated solid-solution unknown phase. Bystrom [23] heated PbC03 and perovskites Sn02 in air at 700 0 C for several hours. He found Tetragonal Rhombohedral P seudo only free Sn02 and the compound Pb2Sn04. It cubic seems probable that our unknown decomposition N umber a a cIa a a phase was identical with this Pb2Sn0 4' ------1---1 Although a perovskite-type PbSn03 mayor may A A A A not be stable, solid solutions can be made containing 3. 9805 4. 1442 1. 0411 1 4. 0045 4. 1421 1. 0344 2 as much as 70 mole percent PbO :Sn02 in solid 4. 0311 4. 1393 1.0268 3 4.0448 4. 1383 1.0231 4 solution with another perovskite end member. 4. 0838 4. 1054 1. 0053 4. 0817 89. 79 0 b5 4.0827 89.690 6 4.0818 89. 76 0 7 d. PbHf03 4. 1059 89. 74 0 8 4. 1236 89.75 0 9 Shirane and Pepinsky [24] reported on PbHf03. 4. 1385 89. 73 0 10 At room temperature it is antiferroelectric, and iso 3. 956 4. 095 1. 035 11 3. 975 4.064 1. 022 12 morphous with PbZr03' However, at 158 0 C, 3. 984 4.060 1. 018 13 3. 993 4. 051 1. 01 5 14 another slightly altered antiferroelectric phase ap 4. 007 4. 047 1. 010 15 pears and persists up to the Curie temperature, 4. 023 16 4. 026 17 215 0 C, where the material becomes cubic and thus 4. 036 • 18 paraelectric. Shirane and Pepinsky were able to 4. 146 4. 106 0. 991 d 19 obtain these structural and dielectric data, even 4. 137 4. 094 . 990 d 20 4. 125 4.090 . 992 d 21 though their total supply of Hf02 was only a single 4. 103 4.077 . 993 d 22 gram. They were troubled by volatilization of 4. 097 4. 072 . 994 d23 PbO because not enough Hf02 was available to work 3.962 4.117 1. 039 24 4.019 4.128 1. 027 25 out a satisfactory firing procedure. 4. 017 4. 116 1. 005 26 4. 015 4. 108 1.023 27 4. 055 4.115 1. 015 4. 055 89. 78 0 ' 28 3.2. Properties of Solid Solutions 4. 067 89.800 29 4. 074 89. 76 0 30 4. 116 89. 74 0 31 Table 1 gives the compositions, heat treatment, 3. 979 4. 099 1. 030 32 and ceramic properties of the speCImens studied. 4. 002 4.103 1. 025 33 4.024 4. 097 1. 018 34 X-ray diffraction powder patterns have provided 4. 046 89.800 35 the lattice parameters shown 111 table 2. The 4. 053 89. 78 0 36 4.056 89. 78 0 37 dielectric properties at room temperature, the Curie 4. 089 89. 78 0 38 temperature, and the peak dielectric constant for 4. 103 89. 84 0 39 the solid solutions studied are given 111 table 3. 3. 988 4.082 1.024 40 4. 082 4.015 1. 016 41 Table 4 shows the radial coupling coefficient observed 4.034 '42 4.044 89.800 43 for these specimens. 4. 057 89.820 44 4. 071 89. 84 0 45 a. PbTiOa-PbZr03 4. 090 89. 87 0 46 4.099 89. 88 0 47 4. 106 89. 88 0 48 The work on ceramics having compositions in this 4.114 4.084 0. 993 d 49 system has been described briefly elsewhere [7]. 4. 119 4.087 . 992 d 50 However, it will be reviewed here in more compr e 3.979 4.064 1. 021 51 4.004 4. 065 1. 015 52 hensive form. 4. 008 4. 064 1. 014 b 53 4.026 89. 82 0 e 54 As mentioned in the introduction, the properties of 4. 034 89. 78 0 , 55 Pb(Zr,Ti)03 solid solutions were described by 4. 036 89. 82 0 56 4. 059 89.880 57 Shirane and Suzuki [4], and later reviewed by 4. 091 89.90° 58 Sawaguchi [5] . Although PbZr03 is antiferroelectric, 3. 989 4. 061 1. 018 59 its solid solutions with more than about 10 mole 3.998 4.064 1. 016 60 4. 010 4. 070 1. 015 b 61 percent PbTiOa are ferroelectric, as shown in figure 4. 022 89. 7° , 62 4.026 89.88° , 63 3a. A morpho tropic phase boundary occurs near 4.030 89. 82° , 64 55 mole percent PbZr03. Solid solutions richer in 3.918 4. 115 1. 050 65 PbZr03 are rhombohedral (pseudo cubic with slight 3. 969 4. 103 1. 034 66 3. 990 4. 098 1. 027 67 extension along a body diagonal), while those richer 4.011 4. 096 1. 021 68 in PbTi03 are tetragonal with c/a> 1 (pseudocubic 4. 017 4. 098 1. 020 69 4. 048 89.87° , 70 with slight elongation along one coordinate axis). 4. 048 89. 80° 71 4. 055 89. 73 ° 72 The deviations from cubic symmetry for these solid 4. 058 89. 77° 73 solutions are shown in figure 3b. 4. 055 89. 77° 74 4. 070 89.78° 75 Ceramic specim~ns of these ferroelectrics were 4. 109 89. 80° 76 found to have structures which confirmed those • See T able 1 for composition of sp ecimen s. reported by Shirane. The structures of the compo b Predominantly tetragon al with minor content of rhombohedral phase. • Also contained non-ferroelectric phases. sitions studied in this binary system are among those d Although listed h ere for conven ience as t etragonal, c/a< l, the superstructure Jines ob ser ved for these solid solutions have been interpreted for pure PbZrO, by listed in table 2. Although substitution of ZrH for Sawaguchi, M aniws, and Hoshino [18] as indication of a larger unit cell with TiH in PbTiOa caused the Curie temperature of the orthorhombic symmetry. • Predominautly rhombohedral with miuor content of tetragonal phase. solid solutions to diminish without discontinuity, f Probably the limiting rhomboh edral composition. 244 TABLE 3. Dielectl'ic pro perties at room temperature, Curie T ABLI;; 4. Radial electromechanical coupling co fficient (J(r) temperatu,re and peak dielectric constant of solid-solution observed for specimens one week after room-temperal'u,re compositions. polarization under conditions indicated. -- --- Dielcc~ic constant (.) and dissipation factor (DF) Curie point at Polarization at 25° C 1 Me R adial umber a. eo upli Dg cocfTicient N um ~ Field 'r ime ber a 1 kc 50 kc 1 Me 20Mc 1'c m· 1-- --- 1- --;---1----,----1-- --,---1 pera· ~re v/mil min ___~ I DF _ ._ DF _ '_ DF _ '_ DF _____ 1 175 60 0.00 2 150 60 . 07 3 150 GO .27 % % % °C 4 150 60 .39 5 150 60 .39 1 221 5.5 204 I. 1 203 0.64 202 0. 48 420 7900 6 150 60 .35 2 338 1. 4 328 0.83 325 .67 321 .87 405 7800 7 150 60 .30 3 641 I. 4 619 .91 610 .83 605 1.3 400 6900 8 150 60 . 19 4 782 0.36 772 . 48 766 .69 751 I. 6 370 7400 9 150 60 . 18 5 606 .64 599 . 91 585 1. 2 567 2.6 330 8400 10 150 120 .14 6 533 . i4 510 . 96 500 1. 4 489 2.6 350 7900 7 524 1. 6 510 1. 6 499 1. 4 486 2.2 350 4400 11 150 60 . 00 S 388 2.3 373 2.3 360 2. S 339 4.3 320 5400 J 2 150 60 . 10 9 375 1. 6 369 2.0 355 2.8 329 6.2 280 4400 ]3 150 60 .17 10 322 1. 6 322 2. 0 309 2.7 269 4.8 235 3600 14 150 60 .26 15 150 60 .28 11 240 1. 8 235 0.59 233 0.57 23 1 I. 0 365 6100 16 150 60 .21 12 631 0.62 618 .59 6 12 .83 f>03 I. 5 270 6800 17 100 40 . 16 13 941 . il 922 .83 9LO 1.1 887 2.2 255 5900 18 150 60 . 06 14 1110 .63 1100 .83 1070 1. 0 960 1. 9 235 5700 15 1260 1. 0 1230 1. 1 1200 1. 5 1050 3. 0 235 5800 24 J50 GO .00 16 776 I. 2 74 1 1.5 723 2.3 671 4.2 225 4600 20 J50 60 .13 17 475 1. 4 463 1. 4 45 1 2.0 444 3.6 210 2800 26 150 60 . 24 18 214 1. 6 205 1. 4 200 2.3 175 3.1 205 b S92 27 150 60 .33 28 150 60 . 39 0]9 114 0.48 112 0. 25 11 2 0.28 111 O. '18 220 d 1430 29 150 60 . :;5 20 122 .3S 119 .25 11 9 . :37 11 9 .56 230 • JOIO 30 150 60 .27 , 21 137 .45 136 .33 135 .38 J35 .38 225 d 694 31 150 60 . 12 22 134 . 45 ]:12 .25 132 .24 132 . 44 265 "383 '23 145 .91 141 .20 141 . 17 141 .26 310 d 238 32 150 60 .00 :;3 150 60 .16 24 220 4.0 217 0.25 216 0.29 215 0. 50 (400) (0) 34 150 60 .40 25 535 0.24 533 .25 532 . 38 53 1 .56 360 13000 35 150 60 . 38 26 '660 .24 664 .25 660 . 50 654 . 63 330 8700 36 150 60 .36 27 815 .34 802 .33 801 .50 795 1.2 330 8100 37 150 60 .33 28 827 . 45 818 .50 S17 1.0 80 1 1.4 320 8200 38 150 60 .24 29 641 .50 632 l.0 632 1.0 613 2.0 330 8600 30 150 60 . 13 30 502 .67 50 1 1. 1 491 I. 7 472 3. I 300 14000 31 356 . 81 354 1. 2 354 I. 9 329 3.8 225 4100 40 150 60 . 16 41 150 60 .39 32 334 O. ·12 333 0.27 332 0.42 329 0.77 350 8800 42 150 60 .39 33 50i . 26 504 .28 499 . 40 495 .91 330 7100 43 150 60 .34 34 976 .45 962 .50 956 . 77 941 1. 5 300 8100 44 150 60 .32 35 S36 .66 8 14 .66 808 1. I 776 2.2 270 8800 45 150 60 .21 36 717 . 77 701 . 91 686 I. 4 66 1 2.6 270 SGOO 47 150 60 .11 37 645 . 83 629 1. 0 616 1. 5 595 2.9 240 8000 38 554 L 1 545 I. 6 534 2. 2 506 4.2 250 8300 52 150 60 .31 39 406 0.91 399 1. 1 391 I. 9 375 4.2 200 6500 53 150 60 .37 54 150 60 .36 40 465 0.34 461 0.32 460 O. '13 453 1.0 300 7100 55 150 60 .:;5 41 lllO .53 1073 .56 1063 . i2 ]049 I. 5 250 7800 56 150 60 .33 42 941 .91 921 .91 904 1. :; 874 2.2 2GO 8300 57 150 GO .20 43 8GO .91 832 I. 2 815 1. 5 793 2.9 260 11000 58 150 GO . 09 44 792 .83 782 1. 2 762 1. 7 746 1. 2 250 8500 45 611 1. 2 594 1. 4 58 1 2.3 550 1. 8 200 6600 67 150 60 .20 46 552 1. 6 549 2.1 526 2.9 502 5. 5 170 6500 68 130 30 - - - -.- - _. - 47 427 I. 0 423 1. 3 411 2.0 391 1. 4 140 4600 140 b :;0 .33 '48 44 3 I. 2 441 1. 6 429 2.4 406 4.5 160 . 2880 69 130 60 .39 '49 365 0.42 365 0.59 362 O. i7 355 I. 7 180 d ]640 70 130 30 ------, 50 203 . 43 ]97 .59 194 . 83 190 1. 8 200 d l080 150 b 30 .38 71 120 60 .34 051 442 0.50 442 0.62 4~5 0.83 429 1. 4 310 4000 72 120 60 .33 52 845 .56 844 .87 83 1 1.0 SI4 1. 9 280 4700 73 120 60 .33 53 962 .63 963 . 83 948 1. 0 9:32 1. 7 250 4700 74 120 60 .23 , 54 910 .87 917 I.] 898 I. 4 869 2. 1 270 4300 75 90 GO . 19 55 832 .91 827 1. 4 804 I. 9 773 3.6 260 4700 76 140 60 . 08 56 780 1. I 795 1. 6 768 2. 1 733 4.2 260 245 the dielectric constant and the radial coupling co ing. Figures 9 and 10 show the variation of piezo efficien t at room temperature exhibited a pronounced electric properties with temperature for two composi maximum as the composition approached the phase tions near the phase boundary. The values plotted boundary, as shown in figure 4. The compositions in th ese figures are given in tablc 5. 52.5 and 55.0 mole percent PbZr03, close to the As still more PbO:Sn02 was added, the solid boundary, approached 0.4 radial coupling coeffi cient solution became incomplete. Ceramics rich in value. Room temperature polarization of the solid PbO:Sn02 consisted of a ferroelectric peroYskite solutions rich in PbTi03 had little, if any, effect. phase and one or more n onferroelectric phases which The coupling coeffi cient, frequency constant, d31, served as diluents. Although the composition with and g31 ar e plotted in figures 5 and 6 as a function 75 mole percent PbO:Sn0 2 still had a ferroelectric of temperature for the two compositions near the type hysteresis loop, the value of the peak dielectric phase boundary. The values plotted in these constan t at its Curie point was much lower than figures are given in table 5. The radial coupling usually observed for a good-quality ceramic consist coeffi cients at room temperature for the limiting ing of a single ferroelectric phase. The diluent rhombohedral and the limit ing tetragonal composi phases consisted of fluorite-type PbO:SnOz and, in tions were high. That of the limiting rhombohedral some instances, free Sn02. Evidently this composi composition, 55 mole percent PbZr0 3, remained tion exceeds the limit of solid solubility of PbO:SnOz relatively high at elevated temperatures. It was in PbTi03. still over 0.3 at 275 0 C, although limited experimen ts N omura and Sawada [26] reported on solid solu indicated that the original properties were not fully · tions of PbO:Sn02 and PbTi0 3. Although difficul regained upon cooling from the high temperature. ties were enco untered in translation from the The value for the room temperature radial coupling Japanese, it would appear that our results and theirs coefficient shown for this specimen in tables 4 and 5 differed in certain respects. They reported limited are slightly different. The slightly lower value solid solubility when PbO:Sn02 exceeds 75 mole shown in table 5 is due to an aging eff ect on the percent; our results concur. However, the ~- did not specimen. Additional refin ement of composition to observe any morpho tropic transition ncar 55 mole approach the boundary more closely might yield percent PbO:Sn02. The di electric cons tan t values still better properties, but was not attempted here. they reported for solid solutions containing less than The di electric constant and the resonance fre 75 mole percent PbO:Sn02 are so low that one migh t quency are both sensitive indications of polymorphic assume that appreciable loss of PbO by volatilization inversion . They indicate, for these compositions, occurred. As an example, their equimolar composi no inversions below tli e Curie temperature (unless tion had, at room temperature, a dielectric constant they occur below - 500 C, the lower limit of our of about 100. Our measured values for ceramics of dielec tric tests). like composition were n early 900, and the composi b. PbTiOa-PbO:Sn02 tion was found to be near the phase boundary. At the Curie point, the differ ences are even more striking NIanv similarities were observed between the effect Our peak dielectric constant for the composition with of PbO·:Sn02 and that of PbZr03 when added in solid 50 mole percent PbO:Sn02 was almost 6,000. The solution to PbTi03 • For the Pb(Sn,Ti)0 3 series, peak dielectric constant observed for this composi also, the presence of a morphotropic transformation tion by Nomura and Sawada was only about 800 at somewhere between 55 and 60 mole percent PbO: the Curie temperature. Sn02 was indicated. As SnH replaced TiH in PbTi03, the tetragonal cia ratio diminished from c. PbZr03-PbO:Sn0 2 1.06, becoming 1.01 for the composition con taining X-ray diffraction powder patterns of PbZr03- 55 mole percen t PbO:Sn02. For the composition PbO:Sn0 2 solid solutions revealed that PbO:Sn0 2 is containing 60 mole percen t PbO:Sn02, however, a soluble in PbZr03 up to the maximum proportions pseudocubic perovskite structure was indicated by tried, 70 mole percent PbO:Sn02. At the tempera the diffraction pattern. The lX2 peaks usually ob tures necessary to produce low-absorption ceramics, served for a cubic structure were not visible. Ob there was no observable tendency toward dissocia servation of ferroelectric hysteresis loops by the tion to eith er Pb2Sn04+fl'ee Sn02 or to a flu orite-type usual method l25], and of the other dielectri c and lead stannate. piezoelectric properties, made it clear that the true The structures of the solid solutions " -ere single symmetry was really pseudocubic rather than cubic. phase perovskites. They appeared to be isostruc Figure 7 shows how the substitution of PbO:Sn 0 2 in tural ·with PbZr03 and sh owed similar superstructure PbTi03 reduces the Curie tcmperature_ It is also, lines. As SnH replaces ZrH in the lattice, the in a rudimentary way, an indication of the solid-state primitive pseudo tetragon al cell size decreases, and its phase diagram. cia ratio, which remains less than one throughout, As further evidence of the existence of th e morpho approaches closer to unity. Simultaneously, the tropic transformation, it may be seen in figure 8 that Curie temperature increases, although the magnitude the room-temperature dielectric constant rose to a of the peak dielectric constant diminishes greatly. sharp maximum as the composition approached that Kittel [19] h as pointed out that a high peak dielectric of the phase boundary. H ere, too, maximum values constant at the Curie temperature is not a necessary of coupling coefficient were observed. They were condition for an tiferroelectricity. It is felt that this less than 0.3. In this respect they are not outstand- series illustrates his point. 246 TARLE 5. Electromechanical properties at elevated temperatures of selected specimens of compositions close to l1wTphotTopic solid solution phase boundaries. The properties listed are the mdial coupling coe.Oicient (kr ) , the frequency constant (f. c., radial 1'esonance fTeq uency multiplied by disk mdius), and the d31 and g 31 piezoelectric constant 'r crnpcrature, O C Structure and COIl1 PO ~ )/0' 1 silion ~'~i)~ ---1,------,.------;------;--1 ---;-1 -1;-----;-1--,----,- ___ ~~~~~~~~~~ 275 0 ~~ ~50 0_ 4 tetragonal k, O. ~R 0. 40 O. ;1S 0.40 0.37 0.35 0.32 b 0.24 o 28 0.26 0. 16 PbTi03 47.5 I. c. .1132 1132 JU5 138 1145 1152 1161 Jlu9 1169 1184 1188 PbZr03 52.5 d 3l 67 74 7:J 78 76 7.) 73 63 (,) ~31 9.8 9.6 9.0 9, 1 8.0 7.3 6.0 4.0 ('J 5 rhomboheclral dO.36 0.37 0.37 O. as 0.37 0.37 0. 36 0.36 0.34 0.33 0.30 0.27 o 21 O. J3 1080 1074 1063 1055 1050 1043 1042 1039 1038 1038 1041 1046 1051 IOS7 P bTi03 4.\ .16 64 70 74 77 8 1. 87 94 98 110 117 127 .1 ;j[ ('J PbZr03 55 JI. 7 12.2 11. 9 11.8 11. 2 10.6 9.6 8.6 7.6 6.3 5.0 3.5 2. I ('J 15 tetra gonal 0.25 0.2G 0.26 0.24 0.22 0.20 0.17 0.07 1152 1l~8 114 1 1149 1159 1166 l1S3 1263 PbTi03 4.\ 46 54 57 55 57 56 58 27 PbO:SnO, 55 5.1 'I. 5 4.1 ~. 5 3.0 2.4 1. 6 0.5 10 pseudo 0.20 0.21 0.21 0.21 O. JS 0. 17 0.12 cubic J 17 l 11 54 1H6 H40 1145 1156 Jl95 PbTi03 41l 28 ~6 40 45 48 48 44 PbO :SnO, (;0 5. 0 4.5 4.2 3.6 2.6 2.2 1.2 27 tCI)'n~onf1 1 O. ~:l 0.33 0.32 0.30 0.29 0.2S 0.27 0.26 0.2,1 0.23 0.21 O. 14 PbTi03 '19.. 1 1142 JI·I() 114 2 JI 5,5 1163 Jl7 1 1179 J 183 1186 11 85 1183 J 186 PbZr03 40.5 60 (1·1 55 60 60 58 59 (;2 PhO:S nO, 10. () 7.8 7. -4 7.1 6.4 n. I 5. .5 5. 1 4.5 23 rhomboll erlra l 0.39 0.40 O. ~9 0.39 0.39 0.37 o 35 0.33 0.31 O.2g 0.2S 0.25 PbTi03 47.2.5 J 11.1 1 1:13 J 130 1123 H31 ] 13J Jl39 1149 1I5G lI (il Jl(il 1 157 PhZrO 42.7.1 62 68 71 76 77 80 82 81 89 95 109 (,.) PbO:S nO, 10.00 9.7 9. 'I 8.\) 8. 4 7. 9 7. 0 G.2 .1.4 '1. '1. 3.5 2.7 ('J (elra~o n a l k, O. ~9 o 39 0.38 0 .3S 0.38 0.30 0.34 0.33 0.30 0.2.1 0.21 PbTi03 48.0 I.e. Jl2S Jl22 lllS 1118 !l21 Jl28 I J40 J 147 J 1.\1 J 152 HS.1 PhZr03 no <1 31 72 75 78 82 85 85 87 92 9(i I 10'1 102 PbO:SnO, 20.0 g 31 9.2 8.5 8.4 7.5 7.0 G.2 5. 4 '1. 6 3.8 2.6 2.3 rhombohedral O. J8 O. ~9 0.39 O. J8 0.3S n.37 O. ;j(j 0.35 0.30 0. 18 PhTi03 46.0 11 39 lI25 112'1 112D J 122 1120 11 J9 1110 ] 12:1 112£i PhZr03 34. () (H (is 72 75 in 8 1 88 102 108 92 PhO:SnO, 20. () 9.. 1 9.0 8.8 8. 1 7. G 6.8 6. I 4.9 3. (l 1. 5 tetragonal k, 0.4U o 39 0.39 0.38 0.35 0.3 1 0.32 o 2~ 0.2il 0.18 PhTi03 47.25 Lc. 1 n3 J 12S 11:32 Jt:J 42 rhombohc tetragonal O. ~6 o 35 0.34 0.3'1 0.32 0.30 0.29 0.25 0. 17 PbTi03 4G.5 J 106 J 108 H OS 1111 IJ 20 1127 1132 J139 J1 !)O PbZr03 13.5 63 70 72 75 73 73 75 7::i fJ7 PhO:SnO, 40.0 8.2 7.5 7.1 6.7 5.4 5. 4 4.8 ~. 'I 1.7 54 rhombohc Ira.] 0.36 O. ~5 O. ~6 0.35 0.34 0.32 0.31 0.23 O. lei PbTi03 45.0 1098 lO93 1090 1089 1002 lOgO 11 04 J 122 II(i8 PbZrO, 15.0 01 6J fi9 72 75 75 83 79 M PbO:SnO, 40.0 8.9 7.8 7 6 7. I 6.3 5.5 4.6 2.5 1. 2 09 tetragonal 0.37 O. :36 0.36 0.3(i 0.36 0. 34 0.33 0.32 0.29 0.27 0.23 0.20 PbTi03 52.5 1110 11 10 H06 H OS 11 J2 1119 1125 H 30 J 133 J 131 !J30 1201 PbIlf03 47.5 59 60 63 66 69 6, 74 74 (,) 8.8 8.3 8. I 7.7 7.3 6. 4 5.4 'I. 9 ('J 70 rhombohedral 0.38 0J8 0.37 0.38 0.38 0.37 0.36 0.34 0.33 0.31 0.24 0.09 PbTi03 50 1I1i 1097 1097 1089 1089 1088 1086 1088 J086 10S9 J 103 H 37 54 60 61 66 71 75 80 92 (c) PhHr03 50 10. ~ 9.6 9.2 9. I 8.5 8. 2 7. 1 5. 7 ('J I~ l"ni ts: kr dimensionless. f. c. cycle-mcters=kilocyclc millimeters. (i3, m/v(xlO- 12J or coulombs/n ewton (XlO-12J. g" voltmeters/newton (X 10- 3J. b Low value probably ca used by eit.h er experim ental error or minor cross co upling to some fl exure mode. c Large dielectric losses prevented dielectric constant measurement necessary to obtain these values. d YaluC's were measured after vary in g Limos of storage. An at-tempt was made to observe hysteresis loops. PbZrOr PbO:Sn02 solid solutions crystallize in a With GO-cycle alternating fields of about 80 volts single antifel'roelectric pe['ovskite solid-solution phase. RJ\IS PCl' 0.001 in. , the patterns produced for these specimens at room temperature were those of lineal' d. PhTi03·PhZr03- PbO;Sn02 dielectrics. Because they are isostructural with Ceramic specimens of these ternary solid solutions PbZr03, show dielectric constant maxima, and have wore examined by X-ray diffraction powder analyses. no dielectric hysteresis, it must be concluded that the The solid solutions riell in PbTi03 were tetragonal 3;)8423-55--2 247 with cia> 1. If a sufficient quantity of PbZrOa plus PbZr03 were not matured (See table 1). There was PbO:Sn02 was added in any proportion, the tetrag no apparent reason for this; volatilization was low onal phase was replaced by a rhombohedral one and there was no evidence of other dissociation. with a< 90 0. These lattice parameters are shown The materia13 remained single-phase perovskites. in table 2. Thus, the phase boundary that charac Because the fired density of these compositions may terizes both the PbTiOa-PbZr03 and the PbTiOa- be less than optimum, their dielectric and piezo PbO:Sn02 systems persists into the ternary field and electric properties probably do not adequately runs smoothly from one binary phase boundary to repre8ent those of the composition itself. the other, as shown in figure 1. The areas of stability As the phase boundary is traced from the of the various phases at room temperature can also Pb(Ti, Zr)Oa composition at 55 mole percent PbZrOa be seen in this diagram. Along this morpho tropic toward the Pb(Ti,Sn)Oa composition at 55 mole boundary, the dielectric constant and the radial percent PbO: Sn0 2, the dielectric constant, shown in coupling coefficient were enhanced, as can be seen figure 12, and the radial coupling coefficient values, from tables 3 and 4. shown in figure 13, remain high through 30 mole Because the PbZrOa-PbO:Sn02 binaries were anti percent PbO: Sn02, then diminish, for reasons stated ferroelectric, there must be another morpho tropic in the preceding paragraph. The maxima on both boundary between that phase and the rhombohedral of these figures help delineate the phase boundary. one. This does, in fact, exist. As found by In the region where the coupling coefficient is high, hysteresis studies at the 30 mole percent PbO:Sn02 it can be noted that addition of PbO: Sn02 tends to level, the compositional position of this boundary increase the room-temperature dielectric constant. seems to be slightly temperature dependent (fi g. 11 ). For a given value of coupling coefficient, this would The composition with 56 mole percent PbZrOa tend to lower g31 and raise dal , because K 2 equals the remained ferroelectric from - 50° C to the Curie product of g, d and Y. Therefore, at room tempera temperature, 140° C. A composition containing ture, tbe rhombohedral binary composition 55 mole 59.5 percent PbZr03 remained ferroelectric up to percent PbZrOa has the best g3l value, while the about 125 0 C, then became antiferroelectric, and tetragonal ternary composition with 30 percent remained so up to 160 0 C, its Curie temperature. PbO: Sn02 and 22.75 percent PbZrOa, has the hi ghest At the 63 percent PbZr03 composition, antiferro d31 constant. High d constant is important for a electricity existed from - 50° C to its Curie point. transducer used as a driver or generator of motion; For the composition with 59.5 mole percent PbZrOa, hi gh g constant is important for sensing elements at temperatures in its antiferroelectric range, anom where motion or force must be converted to an elec alous hysteresis loops of the type first described by trical signal. However, even though optimum d Shirane, Sawaguchi, and Takagi [17] were obtained. constant may be important, the decrease in Curie These are characterized by a linear central region temperature that accompanies substitution of Sn4+ which opens up to two minor loops, one at each for Zr4+ in this system must be regarded as a dis extreme. This type of loop shows the existence of a advantage offsetting the increase in d31 • ferroelectric phase at an energy level slightly above Figures 14 and 15 show the dependence of the the antiferroelectric phase. Instantaneously during electromechanical properties of compositions on the each cycle the crystal becomes ferroelectric when a join containing 30 mole percent PbO: Sn02 with threshold voltage is exceeded, then becomes antiferro 22.75 percent PbZr03 and 'ivith 24.5 percent PbZr03, elec.tric when the instantaneous voltage diminishes the limiting tetragonal and rhombohedral composi agam. tions respectively. The values plotted in these In a narrow region along the rhombohedral edge figures are given in table 5. For all the boundary of the phase boundary, the X-ray powder patterns compositions, no ferroelectric-ferroelectric polymor phic phase transformations were noted at tempera showed a small content of the tetragonal phase, tures below their Curie point. Thus, there are no in addition to the major rhombohedral phase. It is major irregularities in the curve of resonance fre not clear whether thi" represents equilibrium or dis quency as a function of operating temperature. In equilibrium for these specimens. A smooth curve fact, figure 15 shows that the resonance frequency has been drawn through the Curie temperatures of the composition with 30 mole percent PbO: Sn02 obtained ncar the morpho tropic ferroelectric phase and 24.5 percent PbZrOa only varies about 2 percent boundary in figure 11, because the data were not between 25° and 225° C. This is characteristic of sufficient to attach any significance to the spread of all the limiting rhombohedral compositions in this values. system. A comparison of figures 14 and 15 with It was found that the specimens of compositions figures 5 and 6 will bring out the effects of the adjacent to the phase boundary, and containing 40 PbO: Sn02 substitution for PbZrOa in this system. and 50 mole percent PbO:Sn02, were very difficult to mature, even though many heat-treatment schedules e. PbTiOa·PbHfOa were tried. The boundary compositions on the 40 Specimens of PbTiOa-PbHfOa solid solutions were mole percent PbO:Sn02 level with 13.5 percent made in ceramic form. Here, too, a morpho tropic PbZrOa and 15 percent PbZrOa, were made with inversion was observed somewhere between 47~ and fairly low absorption only after repeated heating; 50 mole percent PbHf03• Structurally, composi the compositions on the 50 mole percent PbO:Sn02 tions in this system proved to be very similar to those level with 6.25 percent PbZr03 and 7.5 percent in the Pb(Zr,Ti)0 3 series. Increasing content of 248 lead hafnate, as it replace lead titanate, lowers the po ition clo e to a morphotropic pha e boundary, Curie temperatuTe and, at room temperatme, de exhibit high dielectric con tant and relatively good creases the tetragonal cIa raLio. The equimolar piezoelectri c properties. Furthermore, if polymor composition was predominantly rhombohedral with phic inversion below the Curi e temperature do not a small con ten t of the tertagonal phase. Solid occur, the de irable properties are stable over a wide solutions richer than till in PbHf03 were rhom range of temperature. Examples of this phenomena bohedral. It is recognized that other morpho tropic have been ob erved for the solid solution series phase boundaries may exist for compositions high in PbTi03-PbZr03-PbO:Sn02 and PbTi03- PbHfOa. PbHf03, but they are out ide the range of composi tions investigated. Figure 16 shows the locus of the 5. References Curie points for the various compositions, and is a [1] H . D . Megaw, Origin of ferroelectricity in barium t ita first approximation of the solid-state phase diagram. nat e and other perovskite-type crystals, Acta Cryst. [6] 5, 739- 748 (1952). As the composition approached the morphotropic [2] H . Jaffe, Titanate ceramics for electrom echanical pur phase boundary, the room-temperature dielectric poses, Ind. Eng. Chem. [2], 42 264-268 (1950). constant and the radial coupling coefficient become [3] G. Shiraneand K . Suzuki, Crystal structure of Pb(Zr-Ti) Oa, maximum, as indicated in figure 17. Here, too, J . Phys. Soc. Japan [3] 7, 333 (1952). [4] S. T . Bowden, The phase r ule and phase reactions, radial coupling coefficient values of almost 0.4 were (Macmillan and Co., L td ., London, 1945), p. 167. observed. Specimens of these Pb (Hf,Ti)0 3 com [5] E . Sawaguchi, F erroelectricity versus antiferroelectricity positions had relatively high leakage during polar in t he solid solutions of PbZrOa and PbTiOa, J . Phys. ization, presumably because of their F e20 3 content. Soc. J apan [5] 8, 615- 629 (1953). [6] B. Jaffe, R. S. R oth, and S. Marzullo, Properties of The magnitude of the polarizing field (table 4) was piezoelectric lead zircon ate-lead titanate solid solution varied to accommodate specimens of different qual ceramics, Am. Ceram. Soc. Bull. [3] 33, Program p. 41 ity. As a result, comparison between pecimens of (1954) Abstract Only. a series of compositions is hindered. It seems clear, [7] B. Jaffe, R . S. Roth and S. Marzullo, P iezoelect ric prop erties of lead zircon ate-lead titanate solid-solu tion however, that decirable value of coupling coefficient ceramic, J . Appl. Phys. [6] 25, 809- 810 (1954). typify the boundary compositions. Figures 18 and [8] . R oberts, Dielectric properties of lead zirconate and 19 show the change of the piezoelectric properties of barium-lead zirconate. J . Am. Ceram. Soc. [2] 33, the boundary compositions with temperature. The 63 (1 950) . [9] G. R . Shelton, E. N . Bun t in g, B. J a ffe, and L. Kopell, values plotted in these figures are given in table 5. Unpublished 1951- 52 progress reports. Additional experiments to make these specimens [10] W. P . Mason , P iezoeleetri c crystals and t heir appli ca with a highly-pure grade of Hf02 proved to be dis tions to ultrasonics, (D . Van I ost rand Co., N ew York, appointing. The specimens were difficult to mature, N. Y., 1950). [11] G. Shirane, S. H oshino, and K . Suzuki, Crystal struct ure and inferior values of dielectric con tant and coupling of lead titanate and of bari um-lead t itanate, J . Phys. coefficient were obtained. Soc. J apan [6] 5, 453 (1950) . [12] S. V. Naray-Szabo, Structure of ABOa compounds-sister st ructures, N aturw. [39/40] 31, 466 (1943). 4. Summary [13] S. S. Cole and H . Es penscheid , Lead titanate; crystal st ructure, t emperat m e of formation , and specific grav It has b een observed that the dielectric constant ity data, J . Phys. Chem. [3] 41, '145- 451 (1 937). and the radial coupling coeffi cient exhibit maxima at [14] S. R oberts (private co mmunication , Aug. 1953) . compositions approaching the morpho tropic bounda [15] S. V. amy-Szabo, The struct ure t ype of perovskite ries, an effect similar to that observed at polymorphic CaT iOa, at urw. [16/18] 31, 202 (1943). [16] S. Roberts, Dielectric properties of lead zircon a te and phase boundaries. Electromechanical properties as barium-lead zircon ate, J . Am. Ceram. oc. [2] 33, 63 a function of temperature are summarized in table 5 (1950) . for the specimens close to the morpho tropic boun [17] G. Shirane, E . Sawaguehi, and Y. Takagi, Dielectric daries. These compositions exhibit high Curie tem properties of lead zircon ate, Phys. R ev. [3 ] 84, 476 0 (1951). peratures, 175 0 or above and high radial coupling [18] E. Sawaguchi, H . Maniwa, and S. Hoshino, AntiFerro coefficient, greater than 0.33, as observed in all the electric structure of lead zircon ate, Phys. R ev. [5] 83, specimens except those occuring in the PbTi03- 1078 (1951). PbO:Sn02 system. The limiting rhombohedral [191 C. Kittel, Theory of a n tiferroelect rie crystals, Phys. R ev. [5]82,729- 732 (1951) . composition Pb(Ti.45Zr.55)0 3, exhibited a high radial [20] H . D . Megaw, Crystal structure of double oxides of t he coupling coefficient for temperatures as high as perovskite type, Proc. Phys. Soc. London [326] 58, 275 0 O. This composition also exhibits the highest part 2,133- 152 (1946). g 3l constant as measured at room temperature. The [21 ] W. W. Coffeen, Ceramic and dielectric proper ties of the stannates. .J. Am . Ceram. Soc. [7] 36, 207- 214 (1953). limiting tetragonal composition in the 30 mole per [22] I. Naray-Szab,?; The perovskite structure family, cent PbO: n02series exhibits the highest d3l constant. Miiegyete mi h ozlemenyek [1] I, 30- 41 (19,17). The frequency constant is most stable for the limiting [23] A. Byst rom , X-ray studies on lead sesquioxide, Pb20 a, rhombohedral composition on the 30 mole p ercent Arkiv K emi, Mineral Geol. [23] 18A, 1- 8 (1945). [241 G. Shirane and R. P epinsky, Phase t ransitions in ant i PbO:Sn02 level, although all the limiting rhombo ferroelect ric PbHfOa, Phys. R ev. [4] 91, 812- 815 hedral compositions are good . Properties of solid (J 953) . solution ceramics in the system Pb(Ti,Hf)Oa were [25J C. B . Sawyer and C. IT. Tower, R ochelle Salt as a found to be similar to those found in the Pb (Ti, Zr) Oa dielectric, Phys. R ev. [3] 35, 269- 273 (1930). [26] S. Nomura and S. Sawada, Study on t h e dielectric sub system. stances having high perm ittivity (Part III) I. Stud." It has been shown in the presen t study that ferro on t he Solid solution of titanates, R ept. Inst. Sci. and ciectri c solid-solution ceramics, having their com- T echno!., Univ. Tokyo 7, 83- 86 (1953). 249 Pt cOlier 1600 0040 1400 CJ ::;: Pt crucible 1200 .30 (75 ml) '0c 0 u 1000 o u 10 0 N Pt crucible 10 (20 ml) N 800 .20 t; t; pellet W 600 -r--t-:":1-L specimen 400 (1/2 in. diam) .10 FIGURE 2. Cross-section through the platinum crucible 1lsed to 200 fire PbO ceramics. Cross·hatched rectangles represent PbO:ZrO, pellets slightly enriched in PbO necessary to maintain a proper PbO atmosphere. 0 L..-L-....L....-4/--L....J.J..-L-L---L---1---.J0 0 20 40 60 80 100 PbZr03 PbTi03 100 80 60 40 20 0 MOLE PERCENT FIGURE 4. Dielectl'ic constant (.) and the l'adial coupling coupling coe.fficient (k r ) at 25° C and 1 Me, for PbTiOa- PbZrOa solid- solution ceramics. 500 400 <) 0 w a: 300 F,8 ~ I- 100 '3CO • 0.40 +- A~ 1280 .38 ...... 110 10 0 - c ~1260 .36 ;;--." c 0 20 40 80 100 'CO 0 9 (a) g~ " .. ~ . 34 ~ i ~ 12 40 A\ kr 90 c 8 E ~ , ... .32 <> 40·~~-~-'--~-'--r'--'-'- I , --'----,0.08 \ . 1i ~1220 "'0 80 7 - u .3 0 - .0 0 ,~ ' - .--.~ >, 10_: 1200 z ~ '" 70 ] 6 ~ z ::J .28 ,1 ' ~ i" Q. .- FIGURE 3. a-Solid-state phase diagram for PbTiOa-PbZI'Oa F l GUR!'; 5. Piezoelectric properties at elevated temperatures for solid solutions. b-Crystallograph~c parameters shoumg d~s limiting tetrogonal composition containing 52.5 mole percent tortion from ideal cubic perovskile structure, giving deviation PbZrOa+47.5 mole percent PbTiO in solid solulion. of rhomb angles, from 90° in rhombohedral range and tetrag a onal distortion in tetragonal range. These diagrams are adapted from Sawagurhi [5] on lead zirconate·lead titanate solid solutions. P .'paraelectric, cubic; F .·ferroelectric, rhombohedral; Fp.ferro. electric. tetragonal; A. and Ap·antiferroelectric areas. 250 )t 10· 12 ltKyl 1220 0.4 0 13 .38 J>-- ti IZoo 140 0.40 L...... " . 12 1600 "- '!:i .36 kr 1180 130 ~ .34 '" "\ g 1400 10 E, 1160 ~ .32 120 § j ~ A' u ~ 9 U l!:i .3O ~ 1200 .0- .30 ~ 114 0 0 "" 110 .0- u . 28 8 u ..-- 'g Z 1120 100 ~ o !: .26 7 , c 1000 I{) t- ..J "0 FIGURE 6. Piezoelectric propertie& at elevated temperatures Jor OL-~~~~~~L-~~-L== 0 liml:ting rhombohedral composition containing 55 mole o 20 40 80 100 PbO:SnOz percent PbZrO,+ 45 mole percent PbTi03 in solid solution. PbTI03 100 60 60 20 0 MOLE PERCENT FIGUR" 8. Dielectric constant 1 600 1300 )(10. 12 )t10-3 0.30 (;) IZ80 110 9 o 500 .28 'Zi w ::01260 .26 100 § 8 c ~ f c 0 a:: . i ~ 400 ~.24 . kr f ~1240 90~ 7 ~ E "- « 1 .22 ~ ~ 1> a:: 300 ~220 u 80'" 6 w .20 . Q.. g ::2: ~12oo z "'-.. , w 200 ~ .1 8 - 7O~ t- -2.31 , ~ f- " is 0 ~ 1180 u .16 60 u 4 0 E U ..J '"'" . ..-- 251 r 1300 1280 0 .28 110 10 -;;1260 .26 ICID ~1240 ::;".24 ~ u. ~.22 80 ~ 7 800 '220 L> i D g. a-> C).20 k, 70 ~ 6 L ~1200 z , 1.O :; . C'J !! 60 5 ~ ueo ~ .1 8 ~ ~ o o 1; 600 L> u >- 11 60 J .16 « ~ ~ 114 0 ~ .14 0: 8 ;0; 400 0: u.. 11 20 .1 2 30'0 2 ; 11 00 .I0. L-....L...... J....-1._L...--'--'--"---'_L-....L....--'--1._'--I 20 o 50 100 150 zeo 250 300 350 TEMPERAT URE, ·C 200 FIGURE 10. Piezoeiectric pro perties at elevated tempe"atu l'e~ f or the pse1tdocu IJ ic composition containing 60 mole percent PbO:Sn02+40 mole percent PbTiOa in solid solulion. FIGURE 12. Dielectric constant (.) at 25° C and 1 M c for ternary solid solutions containing 10, 20, 30, and 40 mole percent PbO:Sn02' 0.40 J60~---,---,-----,-----,---,---r---, .30 30% PbO: Sn02 J20 u ° 2BO TC Pcubic lO C\J (; .20 ~ 24 0 g Fretr ~ 200 .... 160 .10 120 \ \ \ BO L-__L' __-'-....J...._-'- ___-'- __-'- __~_~ o 10 20 30 4 0 50 60 70 PbZr03 PbTi03 70 60 50 40 30 20 10 0 MOLE PERCENT FIGURE 11. Phases in the solid-solution series of PbTiOa·· PbZrOa at the 30 mole percent PbO:Sn02 level, showing the PbZr03 + PbTi0 3 X ICO (MOLE BASIS) morphotropic boundaries between the ferroelectric tetragonal (F ','r.) ferroelectric-rhombohedral (F rhomb.) and the anti· FIGURE 13. Radial coupling coefficient (k r) at 25° C for ternary ferroelectric area A, as well as the polymorphic boundary of solid solutions containing 10, 20, 30, and 40 mole percent the paraelectric cubic ( P cu bic) perovskite-type field. PbO:Sn02' 252 ------1300 )1.10,12 1( 10- 3 0.40 "J12BO 110 10 .38 600 '"~1260 .36 kr 100 c 9 c . l? l? _ .34 ~ 5 00 , 90 ~ 8 c U , ~1240 0 "- ~ "- " • ~ "- .32 ~ l "- .~ "- PCubic ... O~- ...... Vl220 w lit x X_ x_ " 80 7 . W 400 "-, fL~o ~ ~ .0. a::: ./ '-4 ~ ~ ~ 1 2CO 70 g 6 ::::J , « ~ .28 931 " ~ f- 300 .... ::; , (/) ~ E <1 '~ ~ 11 80 ~ . 26 " ",- 6C 5 a::: : Tc 0 0 ""'" ,..: w 0 (f'--Cf Ftetr : 2 4 z ~ Cl. 200 >-1160 50 ;: 4 ;! 0 .J -' (/) (/) ~ , z ..- "\ z z , Frhomb ~ .22 UJ 0 0 W g: 11 40 ." 408 3 u 100 Q .o/f. C. f- w 0::" .20 ---"0- ---9 ... a: \ -o~ u. 1120 ,3C 2 ",'" .18 0 .lJ. ..1 1100 .1 6 20 0 20 40 60 80 ICO PbHf03 0 50 100 150 200 300 350 PbTi0 3 100 80 60 40 20 0 TEMPER ATURE, MOLE PERCENT FIGURE 1.J . P iezolectric pl'operties at elevated temperatw'es Jor FIGU RE 16. C'urve showing CW'ie temperature ( T c) 0/ ferro for the tetragonal composition containing SO mole percent electric P bTi03-PbHf03 solid-solution ceramics. 'PbO:SnOz and 22.75 percent PbZI'03, near the ferl'oelectric This is an indication of part of the solid state phase diagram. P,ubio-paraelectric; ferroelectric phase boundary shown in the pl'evio1ls jigw'e , F tetr and F rbomb-ferroelcctric. 1600 0.40 1300 ,, 10-12 )1.10- 3 1400 1280 0.40 110 10 0 1200 .30 u ::lE 1260 .38 /cf '~ 100 9 g " 31 '".!; ...... c 100::> " .. '0 u 1240 -.36 "- 90 i 8 ~ c o ~ u. 0 10 w ~ ~ N ' ''. / + 7~ 1220 8.34 ,~, 80 ~ u 800 .20 .... ~ .-/ kr 0 . It) o ,..: '"z / ' g"'-" ~ N Jb z 1200 ".:j .32 70j 6 c « Q. /' 31 .... ~ 15 600 (/) => \ / :-V 0 . 5 z 0 1100 U.30 6C U 5~ W () ~ .J ,..: ,..: j ! \,~- ,. « z 400 / : ·10 () 1160 0.28 50 ~ 4 ~ z « (/) (/) UJ Q: => 5 I e. ' 0 1140 .26 40 u 38 200 w Q: u. -l' 30 2; 1120 .24 O~~~-L~~ __~~~~~ O o 20 40 100 P bHf03 11 00 .22 20 PbTi0 ICO 80 60 4 0 20 0 0 50 100 150 200 250 300 350 3 TEMPE RATURE. °c MO L E PERCENT FIGURE 15. Piezoelectric properties at elevated tempemtw'esjor F IGUR E 17. Dielectric constant «) and radial co1lpling coefficient the 1'homboherlml co mposii1'on containing SO mole percent (kr ) , at 250 C and 1 M c, Jar P bTiOa-PbHf03 solid-solution PbO:SnOz and 21,.5 percent PbZI' 0 3, neal' the ferroelectric ceramics. ferroelectric phase boundary shown in figure 11 . 253 1260 1280 .36 110 10 12 4 0 .38 110 II <.> ~ 1260 .34 100 =- 1220 .34 100 10 c 1240 ~.32 o c ~ .; 1200 :!:.30 9J 9 "w ~ ~ .. ~ "- ~1220 8.30 ~ 11 80 8.26 80 ~ K ~ 1200 '"~. 28 ~ 1\60 ~ . 2 2 "-::> :::; ~ o t'! "- u.26 8 1180 (/) 1140 § .1 8 ..--' 8 ~ 11 60 0 ·2.4 --' z ~ 1120 ".14 .. o w 0: w 5 1140 .22 ::> .. w 8 1100 CI: .10 _a" _ ...o- - .D -- "'O -- .0.. c/ :;: 0: 30'"" "- tI-_-Q.. _. -'>• • • -0. -.:>. _--<1 ".. "rJ 1120 .20 •• p" f. C. lO BO .06 O'. _.c:! . __ o- __ _C> ... . ,I)" 1100 1060 . 1 8 ~0-L..-::5L:0-'-.J100L,,-..L-,!I50:::--'---::2-':00-:--'---::2-':50-:-L..-::3":OO:-.I.3"'5:-:!0 20 . 02 0~~'-~~-:-..L-1~00--'---I~50---'---2 .1.00-L..2-50'-~-3~OO-~3-J50 20 TEMPE RA TURE, °c TEMPERATU RE , °c FIGURE 18. Piezoelectric properties at elevated temperatures f or FIGURE 19. Piezoelectric properties at elevated temperatuTesfor the limiting tetragonal composition containing 47.5 mole the limiting rhornbohedral composition containing eq1dmolar percent PbHfOa+52.5 mole percent PbTiOa in solid solution. amounts of PbHfOa and PbTiOa in solid solution. W ASHINGTON, July 8, 1955. 254