U. S. Department of Commerce Research Paper RP 1776- National Bureau of Standards Volume 38, March 1947 Part of the Journal of Research of the National Bureau of Standards
Properties of Barium-Strontium Titanate Dielectrics By Elmer N. Bunting, George R. Shelton, a'nd Ansel S. Creamer
The results on barium-strontium titanates are given for heat treatments, absorption, shrinkage, thermal expansion, dielectric constant (K) at -60 0 to 85 0 C, and also for Q, the reciprocal 01 the power factor, at 25 0 C for frequencies of 50 to 20,000 kc/s. A few measure ments of K and Q were made at 3,000 me/s. Specimens matured (absorption less t han 0.1
percent) at 1,250 0 to 1,430 0 C. K values ranged from 34, for BaO:4Ti02 , to several thousand
for specimens with compositions on the BaTi03-SrTiOa join. Specimens having the com
position BaO:5Ti02 were unique in that their temperature coefficient of K was practically zero. Q values ranged from 50 to 100 for test pieces containing over 40 percent of BaO, and from 400 to 10,000 for those with less than 40 percent of BaO. K values did not change appreciably with frequency. Linear thermal expansions between 25 0 and 700 0 C ranged from 0.6 to 0.84 percent. Many of these specimens could be used in radio equipment.
I. Introduction carbonates, were used in the preparation of aU pecimens with compositions shown in figure 1. The properties of titanates containing barium Three other grades of titania were tested also. and strontium have been investigated only . recently [1, 2, 3]/ although dielectrics containing titanium have been used in radio equipment since 1925 [4], and the high values of the dielectric constant of'some of the oxides of titanium have been known since 1903 [5]. Many patents have been issued covering the preparation of dielectrics from titania in combination with such oxides as
MgO, Th02, Zr02, Si02 and as titania-filled or Sf 0 0 0 0 0 o 0 873
ganic plastics. Some of the titanates were con 0 0 0 0 spicuous because they exhibited outstandingly 0 0 0 0 0 0 0 0 high values of the dielectric constant [1] . Al 0 0 though many data have been published [1, 2, 3] ~~ 0 0 0 0 0 8T on specific titanates, a knowledge is desirable of the properties of such materials over a wide range of compositions. In 1944 a systematic study of ceramic dielectrics, of which this paper consti tutes the first report, was undertaken at the request of the Army Signal Corps. FIGURE I.- Ternary diagram for th e system 13aO-SrO-Ti02• showing compositions studied. II. Preparation of Specimens BXBaO; 8=81'0; T=TiO,. A stock of titania, designated TMO, together with chemically pure quality barium and strontium The chemical analysis, furnished by the maker,. and some properties of each of the foUl' grades 1 Figures in brackets indicate the iiteratl1l'c referenccs at thc end of th is paper. are given in table 1.
Titanate Dielectrics 337 ------~ --- ~I
T ATILE I.-Composition, specific surface, and crystal form of four brands of commercial tita~ium dioxide, and also the heat treatments and propenl;es of specimens prepared f rom these matenals
Com position a · I ,. R eciprocal D Ie ec,nc ( I)) of con R tan ~ power fae- Grade designation Specific Oryst(ll form' H eat tr e at~~1t s fer 1 br Sbrink· A bscrp· surfaco b age d tion d (K ) at 25 0 tor at 25 0C '1'iO, SiO , AhO, and 1.000 auel 1.000 k c/s k c/s ------._------lVt % lVl % l Vt% cm'ly ° C °C P ercent Percf'nt 1, 100 1, 305 14.1 3. 33 76 182 1'MO ...... __ .. __ . 98.7 0. 25 0. 2 39, 000 Rutilo...... •... { I, ICO 1. 350 IO. (j 0. 72 87 1, 000 1,100 1, 400 17. (j .02 91 5, 200 1,100 1, 305 7.5 10.50 42 7 lVD .. __ ...... 08.7 . 4 . 03 36,000 ____ . do .... ______. { 1, 100 1, 350 9 . .5 9. 62 49 6 1, 100 1, 425 ------7.02 (.) (,) 1, 100 1, 305 18.3 0.00 97 7, 000 R ... ____ . __ . .. __ . .. 9S.2 . 5 . 1 27,000 ____ . do...... { 1, 100 1, 350 19.6 . 01 98 7, 700 1, 100 1, 400 18. 9 . 01 98 8, 800 A -- ...... ----.... --1 98.8 . 2 1. 2 8, 000 Anatase .. ______. 1,400 None 15. 8 . 00 97 4, 700
• Compositions furnished by maker. b Determined by H. L. Blaine w it b tbe Lea·Nurse apparatus, air· permeability m ethod. ' Determined by X·ray diffraction by H . F . McMurdie. d Valnes obtained after final heat treatment. e Conductance too high for measnremont. f Also contains 0.45% alkali.
Weighed batch constituents were added to III. Test Methods distilled water containing a wetting agent (2 drops Absorption was determined by immersing the of aerosol per 250 ml of water), and the suspension weighed specimen in chemically pure carbon stirred for 1 hI' with a high-speed stirrer. After tetrachloride, where it remained while the liquid drying the caked mixture it was passed through a was boiled for 5 hI' and allowed to cool. After No. 50 sieve and moistened with 10 percent, by quickly drying the surface of the specimen, it was weight, of a 2 1/2-percent starch suspension. weighed in a stoppered bottle. Carbon tetra The moist powder was then dry-pressed at ] 0,000 chloride wa.s used instead of water to avoid any Ib/in.2 into cylinders' (5/8 in. in diameter by 3/4 in. hydration of the specimens. Any gain in weight long), which, after drying, were he~te d at ~ , 100 0 was divided by the density of the CC14 in order to to 1,245 ° C for 1 Ill'. These calcmed cylInders find the equivalent gain, had water been used. were pulverized and passed through a No .. 325 P ercentage absorption equals equivalent gain in sieve. After moistening with 5 percent , by weight, weigh t, divided by dry weight, multiplied by 100. of a 2 1/2-percent starch suspension, the powder The percentage of shrinkage was obtained from was dry-pressed at 20~000 Ib/in.2 into the form of the diameter of the mold used, minus the average disks 1/8 in. thick and of various diameters rang- diameter of the matured specimen, divided by ing from 1/4 in. to 1 in. . . the diameter of the mold, multiplied by 100. In all heat treatments, the cyhnders and dlsks The dielectric constant (K ), and the Q-value,2 rested on platinum foil supported by alumina were obtained from measurements on a Boonton plaques. After heating the specimens overnight "Q" meter, type 160- A, whose condenser had to about 1,000 ° C in an electrically heated furnace, been calibrated against a calibrated precision con the ma.turing temperature of 1,250° to 1,430° C denser. This meter was operated in a cabinet was attained in 3 to 5 hI', using a heating rate of controlled a t 25° ± 0.5° C and a relative humidity about 3 deg C a min, and was held for either 1 or of 40 percent, or less. The titanate specimens 2 hI' within ± 5 deg C of the desired temperature. were heavily coated on both sides with a silver The furnace heating chamber was heated on all sides and was uniform in temperature within 2 This \7alu e constitute-s a "figure of merit" in radio-('ircuit design , and ± 5 deg C. All temperatures were measured with when greater than 10, is nearly eqml to tho reC iprocal of the cosine of t he phase angle (8) . lJ igh Q·values for inductors and condensers are necessary calibrated Pt to P t-Rh thermocouples. for good selectivity in tuned circuits.
338 Journal of Research *
paste and heated to 750° C in an electric muffle crysLal tructUl"e. Consequently, matured speci furnace to give silver electrodes about 0.01 in. mens of impure Ti02 did not exhibiLidentical thick. Any extraneous silver on the side of a proper tie , as illustrated by the data in Lable 1. disk was removed with fine andpaper. Speci Such res ults, bowing grade TiVD to be Lhe least mens were kept at a relative humidity of 40 per satisfactory 1'01' preparing cI i('[ectri cs oJ tIl i type, cent or less and at room temperature for several may not warrant the rejeeL ion of a O" iven grade hours and then at 25 ° ± 0.5 ° C for }~ ill· before the for the preparation of dielectri cs that co ntain measurements were made. Disks with a capacity other materials, such as BaO or SrO . In the greater than the capacity used in the variable experiments on three grades (Lable 2), the choice of condenser in the instrument were measured in grade was immaterial so far as the propcrLies of series with a suitable condenser. matured specimens of SrTi03 was co ncerned. The capacitance from which the dielectric con The maturing temperature and oLh er proper tie of stant was computed was determined at 1,000 kc/s, specimens lllay vary considerably fOJ" some speci and temperatures r'tnging from - 60° to + 85° C, mens wh en different grades of TiOz are used. by the resonant circuit 3 capacity substitution In table 3 data are given on the composition, method. The specimens were held between brass heat treatment; absorption; shrinkage; dielee Lric electrodes in an in sulated chamber 1 ft 3 in vol constant (I'0; and Q, the reciprocal of the power ume. Thl chamber could be cooled with dry ice factor , for matured specimens of Lhe LitanaLes or heated by a heating coil, and was controlled to sL udi ed. ± 0.25° C. :Measurements were made at + 40°, + 60°, +80°, + 5°, + 70°, + 50°, +30°, + 20°, TABLE 2.-Propertie 0/ barium and stnntium titanate 0°, - 20°, - 40°, - 60°, - 50°, - 30°, - 10°, and specimens prepaTed jrom thl'ee grades oj commercial titanium dioxide + 10° C. Prior to each measurement, the tem perature of the specimen was maintained con tant 1 feat treat· Dielectric R cc i ~roca i menLS .. (0 of Absorp. constant for 15 or more minutes. Orade of Shrink· (!() al 25° C power 'fiO, age tion fact.or at. 11easurements at a frequency of 3, 000 mc/s were rremp(' )'. I,1"'" and 1,000 25° C and ature l Ime kc/s made on specially shaped spec imens in the 11as a 1,000 kc/s chusetts Institute of Technology coaxial wave Specimens of BaO:'l'iO, guide instrument [6].
Thermal-expansion determinations were made 0 hr Percent Percellt by the interferometer method at a heating rate of '1'.1{0 .. 1,385 2 10.6 O. 05 J,500 100 11"]) ------1, 400 I 10.9 .03 1, 650 74 2}6 to 3 deg C a minute. R ------J, '100 1 6.9 1. 07 1,300 144 I IV . Results and Discussion Speeimcns of SrO:1'iO,
One of the difficulties encountered in the prep TMO...... 1,375 15.2 0.01 264 8.000 II ·])...... 1,400 14 .8 . 01 270 7.600 aration of titanate dielectri cs is the lack: of R...... 1, 400 16.3 .O t 270 8.000 uniformity in commercial grades of titanium dioxide. The foUl" grades investigated varied not Spccimens of 57.4% SrO :TiO,+42.C,% of n aO: 'riO, only in composition but also in grain size and
T MO. . ... 1, 420 13.7 0.00 680 10,000 3 A A llarLl ey oscillator containing a No. 71 tube was used. This was l1'])...... 1, 430 10.7 2.44 655 3t powered on tbe filament and plate by storage batteries . R esonance was R ...... 1,430 9.7 2.22 605 4,800 determined on a loosely co u pled pick·up circui t, tuned b y a precision ca n· denser, and current was indicated by a \Tacu u m therm ocouple, lIsing a galvanometer, lamp, and scale. a A 11 preparations were gin~ n a preliminary calcination at 1,2 ~ 5° C fo r 1 hr.
Titanate Dielectrics 339 TABLE 3.- Composition, heat treatment, absorption, shrinkage, dielectric constant, 1<, and Q, of bodies in tI,e system BaO-SrO-Ti02
Heat treatment Dielectric constant, Reciprocal, Q, of power- Composition weight J(, at 25° C and- lactor at 25° C and- Proporiion 01 NO.1 1\0.2 Specimen end members designation of join
8rO:lZTiO, BaO:18Ti02
Weight W eighl percent percent Percent Percent P ercent ° C ' C hr Percent P ercent 8Tn_.. ______. __ . 100 a ------9.8 90.2 1,100 1,310 1 0. 00 16.2 113 IJJ 114 2,500 3,500 2,000 18B86. __ . __ . ______36 64 6.2 3.5 90.3 1, 100 1,275 1 . 00 16.6 83 82 1,200 5,400 6,700 BT18._ .. ______a 100 9.6 .---.-.- 90. 4 1,100 1.275 1 . 00 15. a 75 8274 74 260 1, 000 7, 000 1
SrO:4TiO, BaO:6Ti02
ST4. ______.. 100 a ------24.5 75.5 1, 100 1,350 1 0. 00 18. a 148 147 152 800 4, 000 1,300 6BS2 ______75 25 6.2 18.3 75.5 1,100 1,310 1 · 01 17.9 120 119 12J 5,400 4, 000 1, 4.00 6B S5 ______45 55 13.2 11.3 75.5 1, 100 1,275 1 .00 17.9 78 77 76 3,400 3, 400 3,900 6B S7 ______.. 25 75 18. 1 6.3 75.6 1, 100 1,275 1 · 06 16.3 53 53 51 > 500 1,550 3, 700 BT6 __ _.. ______a 100 24.3 ------75. 7 1,100 1, 275 1 · 01 14. a 46 45 44 85 400 2, 20 a
) 8rO:3.4Ti02 BaO:5Ti02
5B S8 ______.. _____ 18 82 22. 7 5. 0 72.3 1,100 1,285 1 O. 06 16. 2 44 43 42 265 1, 600 4,000
BT5 ___ 00 __ 00 ______a 100 27. 7 ------72.3 1, 100 1,325 1 .04 12. a 39 37 37 1,500 2, 300 1,300
SrO:2.7Ti02 B a O:4'ri02
4BS8 ______. ____ .. 15 85 27. 4 5. a 67.6 1,100 1,300 1 0.01 16. 4 43 43 42 > 2, 000 10, 000 5, 000 4BS9 ______8 92 30.4 2. a 67.6 1,100 1,300 1 · 01 15.4 37 37 36 > 1,600 2, 400 4,000 B 'N ______00 a 100 32.4 --- - .--- 67. 6 1, 100 1,330. 1 . 03 16.9 34 34 35 > 1.. 600 2,000 3,700 8rO:2TiO, BaO:3'1'i02
S'1'2 __.. ______.. 100. a 0.0 ------39.3 60. 7 1, 100 1,330 1 0. 09 16.3 186 185 185 1, 600 4,500 2,600 B SL_ .. ______84. a 16. a 6.2 33.1 60. 7 1, 100 1,300 1 . 00 19. 1 163 162 161 1,700 2,200 1,000 B S3 : ______66. a 34.0 13. 2 26.0 60. 8 1, 100 1,315 1 .00 19. 9 121 120 119 5, 100 2,100 1,200 B S4 ______. 51. 5 48. 5 18.1 21.1 60. 8 1, 100 1,315 1 . 00 19.2 90 90 90 3,900 2,500 1, 900 B 86 ______39.2 60.8 23.7 15. 4 60.9 1, 100 1, 290 1 . 00 19. 0 75 75 74 3,300 1, 600 1, 600 BS7 __ .. ______.. ____ 28. 2 71. 8 28.0 11.1 60.9 1, 100 1, 260 1 . 01 18. 1 64 64 63 2,900 2,100 2,000 B 88 _____ . ______. 15.9 84. 1 32.8 6.3 60.9 1, lOa 1,260 1 .00 17.4 51 50 49 2,300 1,200 2,000 BS9 __ .. ___ .. ______8. a 92.0 36. 2 2. 8 61.0 1,100 1,260 1 .00 17. 5 49 49 48 > 2, 000 1,200 2,600 BT3 .. ____ .. ______0.0 100.0 39.0 ------61.0 1, 100 1,260 1 .03 17. 4 44 44 43 720 650 800
2SrO:3TiO, BaO:2.2Ti02 I 82T3 _____ .. ______100.0 0.0 ------I 46.3 53. 7 1, 100 1,310 1 0. 02 16.2 200 200 196 450 2, 600 3, 500 B S22. ______71. 5 28.5 13.2 33. 1 53.7 1, 100 1,350 1 .02 17. 9 153 151 ]49 270 650 1, 500 B S23 ______61. 0 39.0 18.1 28.2 53. 7 I, lOa 1,360 1 .09 17. 1 153 150 149 560 680 1,600 B S25 ______. ______49. a 51. 0 23.7 22.6 53.7 I, lOa 1,310 1 . 02 17. 3 148 147 145 1,700 1,500 1,600 BS26 ______.. ______39.5 60. 5 28.0 18.3 53.7 1, 100 1,290 1 . 06 17. 6 134 133 138 600 550 700 BS271.. __ .. ______29.0 71.0 32. 8 13.5 53. 7 1,150 1,295 1 . 00 17. 6 154 153 153 1,200 850 500 B8279.. __ .. ______20.7 79.3 36.7 9. 6 53. 7 1,150 1,295 1 .00 17. 5 210 205 200 500 480 250 BS28 _____ .. ______12.5 87.5 40.5 5.8 53. 7 1, 150 1,295 1 .00 16.9 255 255 255 385 170 90 B S29 ______6. 0 94. 0 43.5 2.8 53.7 1,150 1, 295 1 .00 15.4 215 215 210 130 100 50 B'1'2.2 ___ _.. ______O. a 100.0 46. 3 ------53. 7 1,150 1, 250 1 .00 12.9 97 95 92 140 75 40 .
340 Journal of Resea rch T ABLE 3.-Composition, heat treatment, absorption, shrinkage, dielectric constant, J(, and C), oj bodies i n the system BaO-SrO-Ti0 2- Contintlcd
H f':1 Ltn'alnlCIlL Composit ion weight lYr iecT ric: C,) I1 SLflll1, Rec iproca l , Q, of power K. at 250 C anr]- factor at 25 ° C and - Proprll"tion of No. J No.2 Specimen Ab· Shrink· drsign ation end members sorp of joill t ion age ---·~----~----I----~--·--~---- 50 1.000 / 20, 000 50 / 1,000 / 20,000 kc/s / kc/s kc/s kc/s kc/s kc/s
Ba O:2'1'iO,
I II'eig ht 111'eig ht I percent percent P ercent IPercent Percent / I o c I 0 c I hr I' Percent I' P ercenl I BT2...... 100 49.0 ...... 51.0 1,100 1,290 I 1 .02 16.4 204 200 197 I 100 70 35 I
S['0:'1'iO,2BaO:3'1'iO,
S T ...... •.•...... 100.0 0.0 ------56. 4 43.6 1,200 1,375 2 0.01 15.2 260 260 260 5,500 8,000 10,000 B2S L ...... 89.0 1.1.0 6.2 50.2 43.6 1,100 1,350 1 .01 16.2 260 255 246 370 1,300 7,000 B2S2 ...... 76.4 23.6 13.2 43.2 43. 6 1, 100 1,350 1 .09 16.2 290 285 2 0 500 850 2,400 B2S3 ...... 67. 7 32.3 18. 1 38.3 '13.6 1, 100 1,310 1 .07 17.6 315 310 300 2, 100 1,900 2,400 B2S4...... 57.7 42.3 23.7 32.7 43.6 1, 100 1,310 1 .06 17. 9 380 375 385 1,300 1,000 900 B2S5...... 50. 0 50.0 28. 1 28.2 43.7 1, 100 1,290 1 .02 17.1 460 450 465 1,000 800 500 B2S6 ...... 40.0 60.0 33.7 22.6 43.7 1,100 1,290 1 . 03 18.0 670 660 645 650 520 325 B2S72 ...... 27.8 72.2 40.5 15.7 43.8 1, 100 1, 290 1 .03 17.8 970 950 050 210 190 95 B2S83 ...... 17.0 83.0 46.6 9.6 43.9 1, 100 1,290 1 .04 17.5 1, 090 1, 070 1,070 ]]0 100 45 B2S0 ...... 10.0 90.0 50.5 5.6 43.9 1,200 1, 285 2 .02 15.1 910 895 885 80 80 35 B2S05 ...... •.•...... 5.0 95.0 53.3 2.8 43.9 1,200 1, 285 2 .00 14 .7 45 850 850 80 60 30 B2'1'3 ...... 0.0 100.0 56.1 ------1 '13.9 1, 250 1, 300 1 .01 10.8 OlD 900 890 70 50 25 -- SrO:TiO, BaO:'1'iO, I S 8 0...... ------00.2 9.8 6.2 50.8 43. 0 1,245 1, 385 2 0. 0:3 14.3 300 300 295 5, 000 4,700 10, 000 S B70 ...... 79.0 13.2 44.5 42.3 1,245 1,400 1 . 0:3 15.0 355 355 345 > 2,300 10, 000 10,000 ------20.1 I SBn ...... -.-.-. 72.5 27. 5 18.1 40.0 41. 9 1,245 1,400 1 .03 14.6 415 415 405 > 2,700 8,000 10,000 S B64 ...... ------6·1.0 36.0 23.7 35.0 41. 3 1,245 1, 400 1 . 10 13.3 5]0 515 505 3,000 7,200 10,000 S E 57 ...... ------57.4 42.6 28.0 32.4 39.6 I 1,245 1,420 2 .00 13.7 660 680 670 > 5,000 10,000 0,000 S E 50 ...... ------to. 0 50.0 32.8 2B. 2 39. 0 1,245 1,420 2 .01 14.3 870 900 900 5, 700 8,500 1,700 SB39 ...... ------30.0 61. 0 40.1 22.0 37.0 1,245 1,420 2 . 00 13. 2 1,600 1,600 1,600 2,000 4,500 1, 200 S B 34 ...... 65.2 42.8 to. 6 37.6 1,245 1,400 1 .02 12.5 2,600 2,600 1, 100 1,700 1,800 ------34.8 1 2,600 I fl E32 ...... ------32.4 67.6 44. <\ l B.3 37.3 1,245 1,400 1 .01 12. 5 3,300 3300 3,300 700 1,000 900 S B29 ...... ------20.0 71.0 46.7 10. 3 37. 0 1,245 1,420 2 . 00 12.8 6,000 6,000 6,000 250 550 200
SB26 ...... ------26.8 73. 2 4 .1 15. 1 36.8 1,245 1, 400 1 .00 12.3 7,000 7, 000 7,000 110 380 165 SB23 . ....•..... ------23.8 76.2 50. 1 13.4 36.5 1,245 1, 420 2 .00 12.4 7,500 7,500 I 7,500 30 110 50 S B2L ...... ------21. 4 78. 5 51. 7 12.0 36.3 1,245 1,400 1 .00 11. 7 3,300 3,300 3,300 27 no 45 S B18 ...... ------18. 5 BI. 5 5:3.5 10. <[ 36. 1 1,245 1,400 I .01 11. 5 2, 300 2,300 2,300 30 105 45 SBl6 ...... ]G. 2 83.B .\5.1 9.1 35.8 1,420 2 .00 11 .4 1,900 1,900 1, 000 35 120 00 ---.-- 245 S Bl ...... 10.0 59. 1 1,,245 1 1,385 2 . 08 1,500 1,500 40 110 60 00.0 I :l5.3 / 13.0 I 1,500 I 1 BT ...... ::::J 0.0 I 100.0 65.7 ···· ~~~· I 34.3 1,245 1,385 2 .05 10.6 1,500 1,500 1,500 80 100 50
3SrO:2TiO, BaO:TiO,
BS36...... 40.0 60.0 30.4 26.4 34.2 1,245 1, 425 2 0.02 13.2 300 300 300 15 50 165 B S37...... 29.0 71.0 46.6 19.2 34.2 1,245 1,425 2 .06 14.6 900 900 900 400 850 700 BS375...... 24.7 75.3 49.5 16. 3 34.2 1,245 1,425 2 . 02 15.9 1,600 1,600 1,600 350 700 400 BS38...... 16.3 83. 7 55.0 10. 7 34.3 1,245 1,430 2 .01 13.5 4, 400 4,400 4, 400 35 155 80 BS39...... 10.0 00.0 59.1 6.6 34.3 1,245 1, 425 2 . 00 15.6 2,400 2,400 2,400 50 150 75
S,T,...... ------52.0 48.0 1, 200 1,400 1 0.02 17.5 238 237 238 2, 100 5,000 2,900 7ST ...... •••••...... ••..... 54.0 46.0 1, 200 1,400 1 .00 18.2 257 256 256 4,400 3,900 2,900 t·······------··-- 3S'1' .... _ ...... T········· ······1 58. 0 42.0 1,200 1,400 1 . 00 15.6 196 196 195 3,600 1,900 1,100
Titanate Dielectrics 34 1 The range in composition of the specimens is men ts was varied widely, 1 to 30 hr, a duration of illustrated by the diagram in figure U Some of 1 or 2 hI' was sufficient for calcining the batches the preparations with compositions indicated by and maturing the specimens. Approximate matur points on the join 3SrO: 2Ti02- BaO.Ti02(fig. 1), ing temperatures are indicated in figure 2. even though mature, disintegrated after several months storage in porOllS paper envelopes. As n02 (14.00) stability of capacitors after prolonged exposure to moisture in the air is important, several specimens of SrO.Ti02 and those with compositions repre sented by points on the BaO.TiOz- SrO.Ti02 join were remeasured for K and Q after storage under room conditions for 6 months or more. The values of K and Qhadnot changed,which indicated (1310)Szlj fj Tu (l2.50) fjTz (1290) t hat no disintegration had occurred. (14M)Ss ~ (1375)ST Two objects of the heat treatments were (1) to (13701
expel the CO2 from the carbonates, and (2) to induce reacLions' among the remaining oxides so that mature specimens (less than 0.10 percent of absorption) resulted. Although a single heat treatment sufficed for a few preparations, a prelimi nary heat treatment for calcining most of the SrO batches was necessary. One advantage of calcina BaO tion was the elimination of difficulties experienced FIGURE 2.- 1Vlaturing temperature after sintering.treatment. B= BaO; 8= SrO; T= TiO,. in dry-pressing disks from the extremely fine grained original materials. In calcining the batches, a relatively high tem In the determination of the dielectric constant perature was unsatisfactory. When such tem and Q, the advantage of specimens with low valucs peratures approached those for maturing the disks, of absorption (0.1 percent or less) is apparent from the resulting calcines were -more difficult to pul the data on specimens TJ110 (table 1) , which are verize and to form into compact dry-pressed disks typical for all specim ens studied. Although the than were the calcines produced at temperatures values of K and Q decrease as the absorption in 100°C or more below those of the final heat treat creases, the amount of change in K is much less ments. Possibly an obj ection to calcining at pronounced than that in Q. The values of K were relatively low temperatures is the high shrinkage duplicated usually within 1 or 2 percent, but vari (10 to 20 percent) that occurs on maturing. ations of several percent in the values of Q were Such an objection is more than offset by the not uncommon. ability to produce practically nonabsorbent speci The data in table 3 show the effect of variation mens from these calcines, whereas the "high cal in composition on the dielectric constant (K ). cined" material was mllch more difficult to mature. Values of 91 to 98 f01 mature specimens of titania In this study, over 500 disks were made because of prepared from grades TMO, A , and R, table 1, are the difficulty in finding the narrow range in tem within the range of values obtained by other in perature at which many of the specimens matured. vestigators [1 , 2], for the dielectric constant of such In the second heat treatment for preparation of material. Additions of BaO to Ti02 resulted in (1) mature specimens, the maximum temperature gradually decreasing values of K (at 25 ° C) from varied from 1,250 °C, for BaO : 2.2 TiOz, to 14,30°C 98 to a minimmn of 34 (BaO:4Ti02), followed by fOT specim ens with compositions in the join (2) increasing values of K to a m aximum of 1,500
BaO.Ti02- 3SrO : 2Ti02 (fig . 1). Although the time (BaO : Ti02). The values of K increased rapidly at the maximum temperature of the heat treat- when the content of BaO was increased from 46.3 to 65 .7 percent. • The abbreviated designation of tbe compositio n of specimens is e\·ident By contrast, additions of SrO to Ti02 caused the from a comparison of column 1 with 2 and 3 in table 3. 'rhus, STu is an abbreviation for SrO : 12TiO,. values of K to increase gradually from 98 to 260
342 Journal of Research (8 1'0: 'l'iOz) . Similarly, increasing values of K resul ted from small alterations in the co mposi wc re observed in some specim ens containing both tions in the join BaO : Ti02-SrO :Ti02 , as shown in
BaO and Ti02 when the SrO con tent was incrcased table 3. and the concentration of Ti02 maintained con The dielectric constant (K ), measured at 1 stant. This is illustrated by compositions on the mc/s, was afI ected also by the temperature of the joins B aO: 18TiOz-SrO : 12TiOz, BaO: 6TiOz-SrO: specimens, as indicated by the data in table 4. 4TiOz, and BaO: 3TiOz-SrO: 2TiOz, as shown in The values for 30°, 50°, and 80° C, can be found table 3. However, increasing the content of SrO by interpolation for most of the specimens. Th e with the concen trations of Ti02 constant, but less smallcst variations in K wcre observed for speci than 61 weight percent, caused the values of K mens with binary compositions in th e range 61.0 to increase rapidly to a peak and then to decrease. to 75 .6 weight percent of Ti02 and 24.4 to 39.0 This is illustrated by compositions on the joins weight percent of BaO, whereas the largest varia BaO : 2.2TiOz-2SrO: 3Ti02, 2BaO : 3Ti02-SrO: Ti02, tions in K were found fo r specim ens that had and BaO : TiOz-SrO : Ti02• At 25° C, changes in the compositions r epresented by points in the join dielectric constant ranging from 1,000 to 3, 000 BaO : Ti02-SrO : TiOz•
TABLE 4.- Dielectric constant, at 1 mc/s , jT.om - 60° to +85° C, and tempemtuTe coefficient of dielectric constant at 0° C
Values of K at (0 C') T empera· lure co· Specimen . designation cmciont of J{ at 0° 0
ppm, 'J'iO,(A)b .. ______105.7 104.5 103.3 ]02.3 1Ol.2 ]00.3 99.5 98.7 97.9 96.4 95.1 IH.3 93.3 -850 'l'iO,(R )b______106. 2 104.9 103.6 102.5 10l. 5 100.4 99.3 98.6 98. 0 96.8 95.5 94.0 93.6 ______
STI2 ______131 128 126 123.5 121. 5 120 11 116. 5 lI5 112.5 1I0 109 107 - 1350 18BS6 ______90.7 .4 87.5 86.6 85.8 85.0 84.4 83.7 82.7 81. 6 81. 2 80.4 -830 BTI8 ______80.5 78.9 78.3 77.6 77.0 76.5 7B.0 75.4 74.3 73. 4 73.0 72.5 -750
S'1'4 ______: ______I 6 174 168 J63 159 155 152 149 143 J38 135 131 - 2500 6B S2 ______152 142 138 135 132 J28 126 J23 J18 114 112 110 - 2200 6B S5 ______88. 5 8'1. 7 83. '1 82.3 81. 2 80.2 79.2 78.0 76.2 74.8 74. 2 73.5 - 1300 6B S7 ______56.3 55.8 55. 4 55. 0 54.6 54.3 54.0 53.7 53.3 52.5 52.0 51. 7 51. 3 -650 BT6. ______46.5 46.3 46. 2 46.0 45.8 45.6 45.4 45.3 45. I 44.9 44 . 7 44.6 44.5 -370
5B S8 ______43.1 43.0 42.9 42.8 42.8 42.7 42.7 42.6 .42.5 42.3 42.3 42.2 42.2 - 200 DT5 ______36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 36.7 o 4BS8 ______44.0 43.7 43.5 43.3 43. I 42.9 42.7 42.6 42.5 42. 4 42.3 42.3 42.2 -380 4BS9 ______36.8 36.8 36.8 36.8 36.9 36. 9 36. 9 37.0 37.0 37.2 37.3 37.3 37.4 +100 BT4 ______33.0 33.1 33. 2 33.3 33. 4 33.5 33.6 33.7 33.7 33.9 34.0 34.0 34.0 +260
ST2 ______255 244 233 224 214 206 200 195 189 180 171 167 162 -3000 B SL ______220 207 197 190 183 178 173 168 164 156 149 146 141 -2300 DS3 ______160 151 145 140 135 132 128 126 123 118 114 112 109 -2400 B SL ______112 108 105 103 100 98 96 94 92 89 86 84 82 -2200 BSB ______92. 8 89.5 86.7 84. 5 82.0 80.0 78.5 77.0 76.0 73.5 71. 2 70. 3 69.0 - 1900 B87 ______78.9 76. 3 74.0 72.0 70.2 68.6 67.4 66. 2 65. 2 63.4 61. 8 61. 2 60.3 - 1800 B88 ______55.9 54.8 53.9 53.2 52.6 52. 1 51. 8 51.4 51.1 50.4 50.0 49.8 49.4 -730 B89 ______52.4 52. 0 51. 5 51.1 50.8 50.4 .50. 1 49.8 49.5 49.0 48.6 48.4 48.1 -640 BT3 ______44.6 44.5 44.5 44.4 44. 3 44. 3 44.2 44.1 44. 1 43.9 43.8 43. 8 43.7 -160 821'3 ______274 262 250 240 230 221 213 207 202 193 184 179 173 -3200 B822 ______: ______210 201 191 183 175 ]68 162 158 154 146 139 136 132 -3100 B 823 ______230 216 203 192 183 175 167 161 155 144 134 131 126 -4100 B825 ______211 220 202 190 179 170 162 156 150 140 131 128 122 - 4400 B 826 ______216 198 182 170 159 151 145 140 135 J27 118 115 111 - 4LOO B827L ______. ______- ______303 277 253 230 208 19'1 181 170 160 145 132 127 123 -5900 B8279 ______--- 288 292 296 297 293 284 269 246 226 187 162 152 141 B828 ______227 23'1 239 243 249 252 254 256 256 247 226 214 190 B829 ______174 181 185 192 196 198 201 204 207 216 225 231 230 85.2 86.6 88.0 89.3[ 90. 8 92.0 93.2 94.1 95.1 96.8 98.5[ 99.5 101 ~ ~~ ~~ ~::::::::::::::::::::: ::::::: I 163 I 168 [ 173 I 177 182 I 187 I J92 I J96 200 I 204 I 210 214 221 S(>c footnotes at end of table.
Titanate Dielectrics 343 TABLE 4.-- Dielectric constant, atl mc/s,jTom - 6Go to + 85° C, and lempeTatUTc coefficient of dieleclTic constant at 0° C- Con.
ST . ·.....••...... •• ...... 367 345 330 315 300 290 280 270 261 246 232 226 219 B2SL ...... •...... ~82 359 340 324 309 295 282 271 2110 241 226 221 213 -4400 B282 ...... 479 442 412 386 362 341 320 304 289 270 250 242 229 -5700 m83 ...... •...... 560 505 '160 425 395 370 350 330 317 290 267 258 245 -5600 B284...... 825 710 630 570 520 475 435 405 385 345 310 295 280 -6200 B285...... 1290 1090 g40 820 720 640 570 520 470 420 370 350 320 - 10700 B286...... 1760 1650 1480 1270 1090 970 860 780 700 575 490 450 410 1190 1200 1210 1200 1180 1130 1080 101 5 825 675 610 530 ~~ ~~~ :::::: :::::::::: ::: :: : ::::::: 1 1~~~ 950 980 1010 1025 1045 1055 ]060 1085 1090 980 910 800 B289...... 735 775 81 0 845 880 910 940 970 995 1055 1120 11 55 1125 B2895...... 610 640 G70 700 730 755 780 805 825 870 920 945 9S0 B 2T3...... 600 630 660 690 720 745 780 825 870 900 920 935 980
8 B9 ...... 466 424 397 381 348 343 325 313 303 283 264 256 247 -3800 622 565 520 485 450 422 397 380 362 332 306 297 279 -5000 827 755 690 635 580 535 500 460 430 385 345 330 311 - 7600 i ~~ : ::: :~ : ~ : : : :::::: ::: ::: :::::::1 1415 1210 1020 870 770 690 630 580 535 470 420 395 367 -9200 SB57...... 3000 2150 1500 1210 1020 890 780 710 645 550 480 450 410 SB50 ...... •...... 1 13400 6300 3700 2400 1850 1450 1200 1020 925 750 625 580 520 SB39...... 3200 3450 4000 5800 IJ500 7200 4000 2500 1900 1270 950 850 740 SB34 ...... 3720 3640 3800 4200 [ 5400 12000 10000 5000 3600 2000 l:lW I 1170 970 SB32...... 3340 3300 3300 3400 3800 1 5700 ]5000 11000 6000 2'150 1550 1320 1070 2370 2400 2400 24 50 2800 3600 10000 8500 3200 1820 1370 1190 ~~~: ::::: ::::::::::::::::::::: ::::1 ~~~~ 2230 2750 2750 2750 2750 3200 5000 13800 4700 2360 l R50 14 20 SB23...... 1240 1400 2180 2060 1980 1980 2020 2300 3000 7500 3100 2400 1720 I . ...•• .... SB21...... 14 50 1700 2570 2450 23 50 2350 2350 2350 2600 11000 4800 3500 2170 I...•...... SB18 ...... 1250 1400 1600 1850 2150 2150 2050 2100 2200 3100 8500 5200 3200 I· ...... 81116 ...... __ ••...... 940 1050 1250 2000 18m 1710 1650 1650 1700 2050 7300 6500 3740 I------SBL...... 780 830 900 950 11 00 1700 1600 I BOO 1450 1410 1600 2050 8200
BS37...... 1670 1800 2270 2000 1600 1350 11 00 I 950 820 690 560 500 435 BS375...... 2330 2400 2600 2900 3650 4000 3080 2300 1850 12W 920 820 690 B 838...... 1290 1650 1950 2050 7. JOO 2J50 2300 2600 3300 4320 2380 1950 1420 I ..••••• ... B839...... 1250 1350 1550 1800 24 50 2400 2300 2250 2200 3000 7500 6000 2100 1 805 815 nrr ______860 910 980 1060 1160 1310 1570 1360 I ~OO J330 1440
• For compositions, see tables 1 and 3. b Grade de;ignation (tahle 1).
The effect of temperature, over the range - 60 0 appeared when the con centration of BaO was to +850 C, upon the dielectric constant of speci more than 28 weight percent. Specimen mens in the system BaO-TiOz is illu8trated by BaO :4TiOz (32.4 percent of BaO) had a slightly fi gure 3. In diagram A the negative temperature positive temperature coefficient of K as well as coeffi cient of K for titanium dioxide is indicated the lowest observed value for K , as shown by the by the curve TiOz. It is seen that increasing t he curve BaO : 4 Ti02 in diagram A, figure 3. A content of BaO in the specimens (to approxi further increase of 6.6 percent of BaO resulted not mately 28 weight percent), as in BaO: 5TiOz, only in a higher value of K but also in a slightly resulted in a reduction of the negative tempera negative temperature coeffi cient, as illustrated by ture coefficient . Attention is directed to the curve BaO : 3Ti02 in diagram B . As the concen specimen containing 27.7 perceni of BaO, because tration of BaO increased within the range 39 to the dielectric constant remained unaltered by 65.7 weight percent (BaO:3Ti02 to BaO.Ti02), changes in temperature within the range - 60 0 the dielectric constant of the specimens exhibited to +850 C, as shown by the curve BaO: 5Ti02 • more pronounced changes with temperature as Certain irregularities in the dielectric constant well as increased values of K , as illustrated by
344 Journal of R esearch (A) (a) (c) (D) 1000 I/O 2 BoO:3TiO;: Izmo 900 /1000 ~ la 10(J(X) ~ ~ 800 B 90 9000 ~ 700 7 8000 'tl 80 "- 7000 ~ ~ 600 70 6 l\) 500 50 .\) 60 4000 \) 400 BoO: T/02 ~ 50 *. III BoO: 6 T;Oz BoO:3T/02 3()()0 0-....0-0 0 0 c 0 c 0 , > ~o , c:s ~ <>-<>~ 300 40 lJaO :5 T/02 0--0-0-0-0--o-- 0 BoO: 2 T/O;:
O-O--O-OAl OJ C c lJaO:4 !to, 30 +, ,- 0 - 60'40-20 0 2040 6080 -60 -4O'ZO 0 ZO 40 60 80 -60 -40 -20 0 ZO 40. 60 80 100 120 140 Temp erature, ·C
FIGUR E 3.- Fariation of dielectric constant with temperatw'e, at 1, 000 kc/s, for specimens with compositions in the binary system, Ti02- BaTi03.
diagrams B, 0, and D (fi g. 3) . It should be noted position indicated by points in the join BaO.TiOz- that the scales werc altcred in the ordinate of SrO,TiOz. The cmve wiLh a peak at 41 ° C diagram s 0 and D , because of the high values of [{. (fig. 5) for one of these specimen , SB21 , resembles Other inves tigators [1 , 2J have found consider the cmve for BaO.TL0 2 (fig. 3, D ). It was found able variation in dielectric constant with changes that increasin g the content of SrO in this seri es of in t emperature '~ of specimens prepared from compositions on the SrO.Ti02-BaO.Ti02 join 1'e
BaO.Ti02 • In the present study, diagram D, stilted in decreasing the t emperature at which tue fig me 3, shows the character of the clielectric peak in dielectric constant occurred (fig. 6). Ex constant- temperature curve for these specimens. trapolation of the curve indicates a peak for Although a peak value of 11 ,800 [{ was observed TiOz at 118 ° C, variations of as much as 1,000 or more in the values of [{ were caused by small changes in temperature within the range of 110° to 125° C. The rapid variation of [{ with temperature occurs at a reversible change in crystal structure from pseucloeubic to the cubic perovskite structure [2], indicated by X-ray studies. Additions of SrO to specimens containing BaO
and Ti02, denoted by the joins in the diagram of figure 1, resulted in negative temperature coeffi cient of [{ for most of the specimens, as hown 70
in the last column of table 4. Coefficients were CIa 20 not computed for all the specimens because of the irregularities in the curves of dielectric constant 90 10 versus temperature. :irO 10 20 30 40 SO 60 70 ~o 90 BaO The portion of the ternary diagram in which peaks were observed in the dielectric-constant FIGURE 4.- Rdation between the temperatw'e at which the peak dielectric constant occ urs an d compositions in the temperature curves is indicated in figure 4. These BaO-SrO-Ti02 system . . peaks were a maximum for specimens with com- B ~ B a O ; 8=l:'rO; 'l'= 'l'iO"
Titanate Dielectrics 345 SrTiOa at a temperature of approximately - 240° PeakK C. Similar data by other investigators indicate MmpDC r--'---'--.--'r--.--.---r-~--~-- that this peak is near -260° C [7] . 100 Figures 7, 8, and 9 show the lines of constant values of K at - 60 °, 0°, and + 60° C with varia tions in composition over a portion of the ternary 50 - I i system BaO-SrO-Ti02 • These diagrams indicate --.I X o MOOOr--.---.--.--'.--.--~--~~--~--~-'
-50 IZOOO 5B21 5 1.71- BaO I 12.0 10 5rO I 36.31. TiOz - /00 I /0000 / ° healtng Peak K= 13,800- I x cooling af 41· I I - 150 I {JOOO / I I I -200 I 6000 / I I
4000 20 40 60 60 wI: 10 FIGURE 5.- Variation of the tempera tun at which the peak dielectric constant occurs with composition on the SrTiOa- BaTiOa join.
uses, such as delay lines, the dielectric with zero -20 a 40 80 IZO 160 temperature coefficient is desirable. °C The dielectric constant was not affected by FIGURE 5.- variation of didectric cons/ant with temperature, variations in frequency within the range 50 to at 1,000 kc/s, for specimen SB21 with composition on th f: 20,000 kc/s. It is believed that the slight differ SrTi03-BaTiOa join. ences in observed values of K are within experi mental error. the changes in the values of K that result from simultaneous alterations of both temperature and composi tion. Despite the relatively low dielectric constant (37) of specimens having the composition BaO:
5Ti02 , the zero temperature coefficient of K is noteworthy. It was found, however, that an addition of 5 percent of SrO to this composition led to a negative coefficient, as in specimens 5BS8 (table 4). Specimens 4BS8 also had a low nega tive coefficient, whereas 4BS9 had a positive co effi cient. Thus, specimens having zero tempera ture coefficien t of K are limited in composition to ~~ SrO '------:~--~--:>L-'-..>L..--~---"'----....:.8aO a small region in the vicinity of the composition /0 20 30 4IJ 50 indicated by the point BT5, figure 1. For some FIGURE 7.-Constant K with varying composii1'ons at -60°C.
346 Journal of Research The variation in values of Q caused by altera T ABLE 5.- Dielech·ic constant K, li nd 0, the reci 7) 1'ocal 0) tions in composition and frequen cy is shown by the power factGr, at 25° C and 1 mc/s and 3,000 mc/s Lhe data in table 3. Although most of the speci mens had relatively high values of Q (400 to Specimen designation K at I m e!s Qat 1 mc/s j( ~~~SOOO Q ~,\;12°O
BaO: 3TiO, ...... 43 3,flOO 42 4,,0 B SG ...... 75 2,400 76 52U
B S7 ------71 1,000 74 310
The data ill table 3 show little correlaLion of Q with frequency. In some insLan ces, a specimen had low Q at 50 kc/s and fairly high Q aL 20,000 ke/s, for example, BT6. Often a duplicate speci m en exbibited a high Q at all frequen cies. As an example of the variation in Q values of specimens r eceiving the same preparaLion and h eat treat menLs, Lhe data in table 6 are given. Although 10 20 30 40 50 60 the variation in the dielectric constant is not FI GURE S.- Constant J( with vW'']jing compositions at 0° C. large, Lhe Q values show a very large variation. However, the specimen with Lhe high est absorp 10,000) , those containing more t han 46.0 percent Lion has the lower Q value. The reason fo r of BaO exhibited low values of from .50 to 100. these differences is not apparent, bu t it may be With specimens having a con tan t and relatively connected with a number of factors, such as the low content of Ti02, an increa,se in the concentra- si:'e of crystals and pores, as well as the state of oxidation of the titanium compow1ds. Variations in the proper ties of specimens of the same composition, SB50, which received differen t heat-tr eatments, are given in table 7. These specimens have a fairly large maturing range with mall vari ation in dielectric constant. Simi lar data co uld be given for mos t of the other compositions of low BaO content.
T AB LE 5.- Properties of specimens of SrTi03 , sintcred fo r 1 hI' at 1,245° C and heated at 1,350° C for 1 hr 60 Dielectri c constant ( K ), R eciprocal ( 0) of power 25° C factor. 25° C SrOL-~J~0--~20~~3~0---4~O~~50~~6~0--~ BaO Shrink· ______Absorption age 20,000 50 kc/s 1,000 20,000 FIG URE 9.- Constant J{ with varying compositions c I + 60° C. 50 kc/s ~~~~ k c/s kc/s kc/s tion of SrO was accompanied by increased values Percent Percent 0. 11 ...... 14.8 268 264 260 450 1,350 3,500 of Q, as illustrated in table 3. As an absorption 0.06 ...... 15.0 249 246 243 2, 100 3,200 4,800 of over 0.01 percent was ' attended by a lower 0.05...... 15.0 258 254 249 900 4,000 8,000 O.OS...... 14 .8 253 250 245 J, OOO 1, 350 4,500 value of Q, some of the specimens with absorptions 0.01 ...... 15.2 260 260 260 5,500 8,000 10,000 over 0.01 percent probably exhibited values of Q 0.00 ...... 15.0 252 249 245 900 4, 000 8.000 lower than the best obtainable.
Titanate Dielectrics 347 TABLE 7.-Propcrties of specimens of SB50, sintend at table 5. As most specimens had a dielectric 1,245° C for 1 hr, und heated at 1,350° C, 1,385° C, and constan t th at was too high for determination by 1,420° C for 2 hr this method, only these three specimens were
Dielectric constallt (l() , Reciprocal (0) of power m easured at 3,000 m c/s. I, 25° C factor, 25° C The thermal expansion of the specimens was Heated Absorp.!Shrink· I______2 hr Lion age high , ranging from 0. 59 to 0. 84 percent between _ 1,000 20,000 _ I 1,000 20,000 I00 kc/s I kcls I kc/s 00 kcj kC~J_~~_ ------° C Percent Percent 0.15 1,350 .. ' 0.02 14.3 870 90r 890 2, 900 6,100 1, 600 BoTtO, (X) 1,350 ... .0·\ 14.3 870 890 900 3, 400 5,800 1, 300 1,385 ... .05 14.2 870 870 890 5,400 7, 000 1,600 1,385 ... .07 14.3 870 870 890 5,700 7.500 1,400 1,420 ... .Ol 14.3 860 860 870 2,800 8,500 1, 700 1,420 ... .02 14.3 870 860 870 2,300 7,500 1,200
In the sp ecimens having a high BaO content, and low Q valu es, the varia tions in the dielectric ·c constan t Q v.alues are more nearly equal, as a~ d \he FIGURE l O.- T hermal expansion Jar a specimen oj BaTi0 3 shown by the data' in t ab\e 8. In general, for and for S B 16 (tab le 3) in the region oj the peak dielectric specimens having a low B'aO conten t, the varia constant, over the range 25° to 170 0 C. tions in the dielectric constant, for well vitrified Solid Ii nes fo r dielectric constant and broken lines fo r t hermal expansion. samples, are much less than the variations in the Q valu es, although fo r specimens of hi gh BaO room temperature and 700 0 C, despite the wide content, and low Q valu es, these variations are variation in composition (table 9). Figure 10 m ore nearly equal. illustrates a peculiar feature of the expansion curve for specimens 'With compositions in the join
TAB LE 8.- V ariations in propert'ies of some specimens B aO:Ti02-SrO:Ti02 • The fiat section of these containing over 40 percent of BaO curves occurred in the range of temperature - characterized by a peak in the dielectric constant. Hcci procal ( I)) j . . I Diclectric con· I . of power fac t or ___ . s~~~. ___ ~:~~:t m e~s s~lb~ .:.t ant~~~~~=------T ABL E g.- Linear th ermal expansion dc... .H !- Tem- T CIll- lioll 1 ") natIOn pera. Time nera. Time .50: 000 2~ OUO .\0 1.000 20. 000 LU re t ure kc/s kc s kc/s kc/s kc/s kc/s rr"empcraturc range from 25° C to------Sprrimen des· ignation Per· 100 ° 200 ° 300° 400° r>oo o 600° 700° 800° 900° ° C hr ° C hT cent C C C ceo C C C { 1, 245 J 1, 375 2 0.00 1,930 1,850 1, 810 33 74 60 'S B I6. .. 1,245 1,385 2 . 05 1,890 1,840 1,820 36 112 62 1,245 1,420 2 . 00 1,920 1, 850 1,790 11 9 Per· Per- P er· Per· Per· Per· Per- P er· Per- 36 62 cent cent cent cent cent cent cent cent rent I 1,310 2 . 05 860 830 820 83 61 28 B ,S95 __ { I,200 TiO, _ .. ______. 0.06 0. 14 O. Z3 0.32 0.41 0.50 0.60 0.69 0.79 1,200 1,285 2 .00 840 820 810 74 52 27 B T I8 ------.05 14 .23 .31 .41 .50 . 59 { 1,245 1 1,385 2 . 05 1,460 1,410 1,360 79 93 50 B Tu.. ______'1' ____ . . 05 .14 .24 .33 .43 .54 .64 ------1,245 1,425 2 .08 1,480 1,480 J,41O 82 84 44 B TL ______.06 15 .24 .34 .4.5 .57 .68 ------B t - __ . 1,245 ------1 { . 03 1,690 1, 650 1,670 134 74 28 BT4______.. }1,4oo . 06 14 .23 .32 . 41 .51 .60 .70 ------B t b ____ 1, 245 [ 1. 071,3301 1,300 1,330 98 144 78 BT3 ______.. 1 . 06 .16 . 26 . 37 .48 .59 .7l ----.------I B T2.2 .. __ ...... 06 . 16 .26 . 37 .49 .61 .72 --.------BT2 - BaTiO, made w ith Ti02, grade lI ·D . ------.07 .16 .28 .40 .52 .65 .78 --. ------B T ______...... 05 13 . 25 .38 . 52 .66 . 80 b BaTiO, made w ith T iO" grade R. ------S B 64 .. : __ . __ ... .07 . 18 .30 .42 .55 .67 . 80 ------S B 29 .... ____ ... .07 . 19 . 32 .44 .58 .71 .84 ------.----- Coating the specimens, particularly those h aving SB 20F a ----,.- ,07 19 .29 .41 .54 .68 .79 ------S BI6 .. ____ ...... 04 .16 . 28 .41 .55 .68 .81 ------r elatively high absorption, with wax or paraffin S'1' .... ______. 07 .17 .29 .40 .51 . 63 .74 ------increased the values of Q. The improvement, ST2 .. __ . ____ ... . 06 16 . 26 .36 . 46 . 55 .65 .75 --.--- however , was not permanent, for on standing a ST4 .. ______. '1 .06 .15 .25 . 35 .44 . 55 .65 ------gradual decrease in Q was noted . -3% M gF, added. At a frequency of 3,000 m c/s, a greater difference was observed in the values of Q than of K com Although the construction of a phase diagram pared with their respective values found at a for this system was outside the scope of this 111- frequency of 1 mc/s, as indicated by the data III vestigation, there were indications, based on
348 Journal of Research matming temperatures, of the existence of com- great in some to prevent their use as bypass and \ pounds in various regions of the diagram, figure 2. co upling condensers. A few have positive tem For example, a billary compound in the region perature coefficients, although that of one speci of BaO:4Ti02 is suggested by the maturing tem men (BaO:5Ti02) is practically zero. When perature, dielectric constant, and X-ray spectro properly fabricated, some of these titana t(' bod ies gram. In fact, a comparison of X -ray patterns could be used also as filter or storage condensers, for all the specimen in the system BaO-Ti02 and as delay lines for mi crowave signal indicated the fdnmition of other compounds in addition to BaO:4Ti02 and BaO:Ti02. 5 The ma VI. References turing temperature of 1,350° C fo r specimens in the region 18 percent BaO, 28 percent 81'0, 54 [lJ Eugene ,rainer, High titania dielectrics, Trans. Am. E lectrochcm. Soc. 89 (Apr il 19'16). Prcpri nt 89- 3. percent Ti02 is suggestive of a ternary compound, [2] A. \'on Hippe] alld aswciates, High dielectric con ~ tallt but the suggestion is not supported by data on ceramics, Report VII (Au gust 1944). Titan ia ceram the dielectric constant or by X-ray patterns. ics II, Report XI (October 1945). (Laboratory for Insulation Rescarch, i\ fafs . lnst. or T ech., V. Conclusions Cambridge, Mass.) [3] B. v"ul. Diclectric constantB of some liLanaies, Xa(lIrc Mature specimens (absorption less than 0.10 156, 480 (1945). percent) can be made from mixtures of titanium [4] G rman Patent 5'15,402. dioxide with barium and strontium carbonates, [5] W. Schmidt, Dctermination of di elcclric constants of crystals by mcans of electric wa\'es, Ann. Physik which have compositions represented by point in [14] 9, 919 ( 1902); 11,114 (1903). the system BaTi03-8rTi03-Ti02• The cliclecLri c [6] A. von Hippel, D. G. Jclatis. ancl W. B. Westphal, The constant of these specimens varies from 34 to measurement of d ielectri c constant a nd loss with several thousand, whereas lhe Q values vary from stand ing waves in co-axial wave guides. (April abou t 50 to several thousand. :'10st of these 1943.) (National D ercnse Re ~e arch Commi ttee, Contract OE:\fsr- 191. i\Ias,· . Tn ,L. of Tech.) specimens exhibit a large negative temperature [7] \r. Jackson and W. R cddiph , H igh pcrmiLtivity crystal coefficient of dielectric constant. which is not too line aggregatcf Nature 156, 717 (1945). 'The authors ar0 indebted to lI. F. :lrcl\fur Titanate Dielectrics 349