Feb». 11, 1969 sHxNosU r-'uJlwARA ETAL 3,427,173 CERAMIC DIEL'nc'rRIcs Filed June 8, 1964 / ofZ
FIG. DIELECTRIC CONSTANT@ '
n_MwXw w M„wn_w O/OAm Y mSÃ „Mm„ m.
FIG. 2 Q-VALUES
’à o / o 0A
Luz 03'21'505 M 90"@4' 1o
INVENTORS BY ¿AMM ¿if @fpm ' Feb. 11, 1969 SHINQBU FUJIWARA EVAL ` 3,427,173 CERAMIC DIELECTRICS Filed June 8, 1964 Sheet ë of 2
TEMPERATURE coEr-'EICIENT ¿SEE-Aw 0E DIELEcTRm CONSTANT 3,427,173 United States Patent O ” CC Patented Feb. 11, 1969
1 2 range of 1100“ to 1300" C. for about 2 hours, pulverize 3,427,173 the calcined materials into fa fine powder followed by CERAMIC DIELECTRICS Shinobu Fujiwara, Minami-Akita-gun, Akita-ken, and adding a binder in solid or liquid form, in which the Takao Shiraiwa, Akita-shi, Japan, assignors to materials are not soluble, to bind the powder, and form TDK Electronics Co., Ltd., Tokyo, Japan the powder into disc shape in desired size with sufñcient Filed June 8, 1964, Ser. No. 373,313 pressure for shaping, and then sinter the shaped ma U.S. Cl. 106--39 4 Claims terials in oxidizing atmosphere at the temperature range Int. Cl. C04b 35/46 of 1100 to 1400° C. for »about 3 hours. FIGURE 1 of the accompanying drawings is a ternary diagram representing the relation between the three com ABSTRACT OF THE DISCLOSURE ponents of the ceramic -bodies within the present inven The present invention provides novel ceramic dielec tion, that is, barium titanate (BaTiO3), lanthanum titani tric compositions consisting essentially of a sintered mix um oxide (La2O3-2Ti02) and calcium titanate (CaTiO3) and the dielectric constant e. ture of 45 to 95 molar percent barium titanate, 1 to 20 15 FIGURE 2 is a ternary diagram representing the rela molar percent lanthanum titanium oxide La203~2'l`i02 and tion between the three components of ceramic ‘bodies 1 to 54 molar percent of calcium titanate. The ceramic dielectric compositions are produced by combining bar within the present invention, that is, barium titanate (BaTiOa), lanthanum titanium oxide (La2O32TiO2) and ium carbonate, calcium carbonate, lanthanum oxide and calcium titanate and the Q-value. titanium oxide to `form ‘a homogeneous mixture. Such 20 FIGURE 3 is a `ternary diagram representing the rela mixture is calcined in an oxidizing atmosphere at a tem tions between the three components of the ceramic bodies perature in the range of 1,l00° C. to 1,300° C. for about within the present invention, that is, barium titanate two hours. The resultant mixture is pulverized into a (BaTiOg), lanthanum titanium oxide (La2O3-2Ti02) and fine powder followed by the addition of a binder which calcium titanate (CaTiO3) and temperature coeñ‘lcient of is admixed with the powder. The mixture is formed into 25 the dielectric constant. the desired shape and size and the resultant shape is sin In the present invention, the range of the proportions tered `in an oxidizing atmosphere at a temperature in the of the three components, where the favorable properties range of 1,l00° to 1,400° C. for about three hours. of middle range of dielectric constant, low dielectric loss and good temperature coefficient can be obtained is 30 limited, as can be seen in the diagrams, as follows: This invention relates to an improvement in ceramic di electrics. (Molar percentage) The object of this invention is to provide ceramic di Barro, ______45-95 electrics which have much greater excellence in dielectric La2o3~2~rio2 ______1-20 Cano, ______1-54 constant and Q-value than usual ones. 35 The ceramic dielectrics, which have been widely used, The reasons for limiting the proportions to the said may be classified into two types: the one mainly com values are: When the proportion of barium titanate prises titanium oxide and the other mainly comprises (BaTiO3) is below 45 molar percent, dielectric constant -barium titanate. Titanium oxide type dielectrics, which e becomes very small, and when it exceeds 95 molar per have been widely used as temperature compensator, have 40 cent, Q-value 'becomes extremely low. When the propor high Q-values ranging from 2000 to 3000 at high fre tion of lanthanum titanium oxide (La203 '2TiO3) is below quency, whereas their dielectric constants are small. For l molar percent, the eliect of addition is ineffective and example, the dielectric constant of rutile ceramics which when it exceeds 20 molar percent, vitriñcation is dil'l'lcult. is regarded as a relatively highly practical type among When the proportion of calcium titanate (CaTiO3) is be~ the ceramics is only of the order of 114 or so. 45 low 1 molar percent, the desired characteristics can not On the other hand, barium titanate type ceramic di be obtained and when it exceeds 55 molar percent, dielec electrics have large dielectric constants of more than tric constant e becomes small. 2000, `and low Q~value of about 150 with extremely large The following examples will give a closer insight into temperature dependence and the minimum value of tem the present invention. perature coeñicient of dielectric constant, at the present, 50 is approximately -6000X l0r5/ ° C. EXAMPLE II The characteristic feature of the present invention is a The raw materials employed are barium carbonate type of ceramic dielectrics whose characteristics lie be (BaCO3), calcium carbonate (CaCOa), lanthanum oxide tween those of the two types mentioned above. It has (La2O3) and titanium oxide (TiOg). In the present case, larger dielectric constants than those of the titanium oxide 55 barium titanate (BaTiO3) may be formed by reaction type which have small dielectric constant, and much of a mixture `of barium carbonate (BaCO3) with titanium higher Q-values than those of barium titanate type which oxide (TiOa) `on tiring, calcium titanate (Ca-TiO3) may have large dielectric constant. be formed by reaction of a mixture of calcium carbonate That is, this invention relates to a type of ceramic di (CaCO3) with titanium »oxide l(TiOZ) yon lñring, and electrics whose main components are barium titanate 60 lanthanum titanium oxide (La2O3'2TiO2) may be formed (BaTiOg), lanthanum titanium (IV) oxide (I_a203' from lanthanum oxide (Lagoa) and titanium oxide 2TiO2) and calcium titanate (CaTiOa), and it has di (TiO2) on firing. electric constants ranging from 250 to 3000 or so, Q~ Mix barium carbonate (Ba‘COB), calcium carbonate values ranging from 100 to 5500 and temperature coef (Ca'CO3) and lanthanum `oxide (La203) with titanium ñcients of dielectric constants ranging from -2100X 65 oxide (TiO2) in the following proportion: 10“6/° C. to -9500>