JPH0546686B2 - - 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, porcelain compositions for varistors with capacitance mainly contain SrTiO ₃ and small amounts of Nb ₂ O ₅ and La ₂
Porcelain raw materials containing O ₃ , SiO ₂ etc. are heated in a non-oxidizing atmosphere such as nitrogen gas containing a small amount of hydrogen gas.
It is made by firing at a temperature of 1,300 to 1,450 degrees Celsius, and then firing it in air at a temperature of around 1,000 degrees Celsius. 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 12 to 550 V, nonlinear index α was 10 to 13, and capacitance was 1 to 60 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 ceramic composition according to the present invention contains 100 mol parts of SrTiO ₃ (first component) and one or more selected from the group of La ₂ O ₃ and Y ₂ O ₃ (first component). 2 components) is 0.05 to 7.75 mole parts, and TiO ₂ (third component) is more than the above second component.
0.01 to 2.25 more molar parts and one or more selected from the group of SiO ₂ , Sb ₂ O ₅ , Bi ₂ O ₃ (fourth component)
0.01 to 3.25 mole parts, and 0.001 to 1 or more types (fifth component) selected from the group of NaF, LiF, and KF.
It is obtained by firing in air a mixture consisting of 0.01 mole part and 0.01 to 1.25 mole part of one or more components (sixth component) selected from CuO, CaCO ₃ and ZrO ₂ . [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°C 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%
1.63 g of La ₂ O ₃ powder (per 100 mole parts of SrTiO ₃
(equivalent to 0.5 mole part), 1.81 g of Y ₂ O ₃ powder with a purity of 99.9%
(equivalent to 0.8 mol parts per 100 mol parts of SrTiO ₃ ),
1.60 g of TiO ₂ powder (2.0 g for 100 mole parts of SrTiO ₃
(equivalent to molar parts), 0.14g of SiO ₂ powder with a purity of 99.0%
(equivalent to 0.25 mol parts per 100 mol parts of SrTiO ₃ ), 0.00117 g of 99.0% pure NaF powder (equivalent to 0.003 mol parts per 100 mol parts of SrTiO ₃ ), and 99.0% pure CuO
0.0159g of powder (equivalent to 0.02 mol parts per 100 mol parts of SrTiO ₃ ) and 0.246g of ZrO ₂ powder with a purity of 99.0%
(equivalent to 0.20 mol parts per 100 mol parts of SrTiO ₃ ) was weighed. These were stirred and mixed in a grater 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 about 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 13. Furthermore, Samples 1 to 12 and Samples 14 and 15 in the table below were also manufactured in the same manner as Sample 13 by weighing and mixing the respective components so as to have the compositions shown in the respective columns. 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 15 is 12.3 to 488V, and the voltage nonlinearity index α is
It was 10.1-14.8. Although the capacitance is not shown in the table below, it was 1 to 60 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 SrTiO ₃ is 100 mol parts, one or more selected from the group of La ₂ O ₃ and Y ₂ O ₃ is 0.05 to 7.75 mol parts, and TiO ₂ is from the group of La ₂ O ₃ and Y ₂ O ₃ 0.01 to 2.25 molar parts more than the selected above components, and SiO ₂ ,
0.01 to 3.25 mole parts of one or more selected from the group of Sb ₂ O ₅ and Bi ₂ O ₃ , and 0.001 to 0.01 mole part of one or more selected from the group of NaF, LiF, and KF;
One or more selected from CuO, CaCO ₃ and ZrO ₂
A porcelain composition for a varistor, which is obtained by firing a mixture consisting of 0.01 to 1.25 mole parts in air.