JPH0546682B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to varistors having capacitance.
This invention relates to a SrTiO ₃ based ceramic composition. [Prior Art] Conventionally, ceramic compositions for varistors with capacitance have SrTiO ₃ as the main component, with small amounts of Nb ₂ O ₅ and SiO ₂
The porcelain raw materials containing the
It is made by firing at a temperature of 1000°C and then firing it in air at a temperature of around 1000°C. The characteristics of a varistor made using this porcelain composition are, for example, when silver electrodes are provided on both main surfaces of porcelain formed into a disk shape with a diameter of 8.4 mm and a thickness of 1.0 mm, the varistor voltage V ₁ was 120 to 550 V, nonlinear index α was 10 to 13, and capacitance was 1 to 5 nF. [Problems to be Solved by the Invention] The above-mentioned conventional porcelain composition is obtained through two firing steps: firing the raw material in a non-oxidizing atmosphere and then firing it in air. This type of porcelain composition has a problem of low productivity due to firing, and improvements have been desired. This invention was made to solve the above-mentioned problems of the conventional SrTiO ₃ ceramic composition for varistors with capacitance. An object of the present invention is to provide a porcelain composition for use. [Means for solving the problem] The porcelain composition according to the present invention contains 100 mole parts of SrTiO ₃ (first component), CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ ,
Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂
O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ at least 0.05 to 7.75 mole part of one or more selected from the group (second component), and TiO ₂
(third component) is 0.01 to 2.25 moles more than the second component, and one or more selected from the group of SiO ₂ , Sb ₂ O ₅ , Bi ₂ O ₃ (fourth component) is 0.01 to 3.25 moles part, and 0.01 to 0.5 mole part of Ag (fifth component),
One or more components (sixth component) selected from CuO, NiO, CoO, ZnO, Al ₂ O ₃ , CaCO ₃ are 0.01 to 1.25
It is made by firing a mixture consisting of molar parts in air. [Example] Next, an example of the present invention will be described. First, 147.62g of SrCO ₃ powder with purity of 99.5%, purity
79.90 g of 99.5% TiO ₂ powder was weighed out and mixed by stirring in a ball mill for 10 hours. Next, this mixed powder was calcined at a temperature of 1180℃ for 2 hours, and then ground again in a ball mill for 8 hours.
SrTiO ₃ powder was made. Next, 183.52g of the above SrTiO ₃ powder, purity 99.9%
of CeO ₂ powder (0.258 g for 100 mol parts of SrTiO ₃
(equivalent to 0.15 mol part), 99.9% pure Nd ₂ O ₃ powder
0.505g (equivalent to 0.15 mol parts per 100 mol parts of SrTiO ₃ ) _, 0.523g ( _{SrTiO 3}
(equivalent to 0.15 mol parts per 100 mol parts), purity 99.9%
of TiO ₂ powder (0.799 g for 100 mole parts of SrTiO ₃
0.0856 g of SiO ₂ powder with a purity of 99.0% (equivalent to 1.0 mole part)
(equivalent to 0.15 mol parts per 100 mol parts of SrTiO ₃ ), 0.270 g of 99.0% pure Ag powder (equivalent to 0.25 mol parts per 100 mol parts of SrTiO ₃ ), 0.100 g of 99.0% pure CaCO ₃ powder ( (equivalent to 0.1 mole part per 100 mole parts of SrTiO ₃ ) and 0.0747g of NiO powder with a purity of 99.0%
(equivalent to 0.1 mol part per 100 mol parts of SrTiO ₃ ) was weighed. These were stirred and mixed in a pickler for 20 hours. After adding a binder to the above mixture and granulating it, this was pressure-molded into a disk shape with a diameter of 10 mm and a thickness of 1.2 mm. Next, this molded product is heated in air from room temperature to 1300°C.
The firing profile consisted of heating to a temperature of 1450°C to 1450°C, maintaining this temperature for 4 hours, and then cooling for a total time of approximately 12 hours. The disk-shaped porcelain composition thus produced had a diameter of about 8.4 mm and a thickness of about 1.0 mm. Next, silver paste was applied to both main surfaces of the porcelain disk in a circular shape with a diameter of 8.0 mm, and this was baked at a temperature of 750° C. to provide electrodes. This was designated as sample 22. Further, Samples 1 to 21 in the table below were also manufactured in the same manner as Sample 22 by weighing and mixing each component so as to have the composition shown in each column. For each of these samples, measure the voltage between the electrodes when the current I ₁ = 0.1 mA, that is, the varistor voltage V ₁ ,
Furthermore, the voltage V ₂ between the electrodes when the current I ₂ =1.0 mA was measured, and the voltage nonlinearity index α was determined from these values using the formula below. Also, the capacitance C is expressed as the frequency
Measured at 1KHz. α=log(I ₂ /I ₁ )/log(V ₂ /V ₁ ) Among the measurement results, the varistor voltage V ₁ and the voltage non-linearity index α are shown in the table below. As is clear from the table below, the varistor voltage V ₁ of samples 1 to 22 is 128 to 524V, and the voltage nonlinearity index α is
It was 10.3 to 13.8. Although the capacitance is not shown in the table below, it was 1 to 5 nF.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, a varistor with capacitance can be produced by firing the raw material once in air, instead of firing the raw material twice in a non-oxidizing atmosphere and in air as in the past. This has the effect of providing a porcelain composition for use.

Claims (1)

[Claims] 1 100 mol parts of SrTiO ₃ and CeO ₂ , Pr ₂ O ₃ , Nd ₂
O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ ,
One or more selected from the group of Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ is 0.05 to 7.75 mol parts, TiO ₂ is CeO ₂ ,
Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂
0.01 to 2.25 more molar parts than the above components selected from _the group of _{O 3 ,} Dy ₂ O ₃ , Ho 2 O ₃ , Er ₂ O ₃ , Y ₂ O 3 and SiO ₂ , Sb ₂ O ₅ , Bi ₂ O 0.01 to 3.25 mole part of one or more selected from group ₃ , and 0.01 to 0.5 of Ag.
Molar part and CuO, NiO, CoO, ZnO, Al ₂ O ₃ ,
A porcelain composition for varistors obtained by firing a mixture of 0.01 to 1.25 mole parts of one or more selected from CaCO ₃ in air.