JPH08726B2 - High-permittivity porcelain composition for temperature compensation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is used for temperature compensating porcelain capacitors and the like.
The present invention relates to a high dielectric constant porcelain composition comprising a binary solid solution of CaTiO ₃ —SrO · Nb ₂ O ₅ .

[Prior art]

Conventional porcelain compositions for temperature compensation include CaTiO ₃ and SrTiO ₃ .
_{3, MgTiO 3, La 2 O} 3 · 2TiO compositions such as ₂ have been used,
These compositions have a dielectric constant ε of 10 to 350 and a temperature coefficient of +100 to
It was in the range of −350 × 10 ⁻⁶ / ° C. However, a disadvantage of these compositions is that the relationship between the dielectric constant at room temperature and the temperature coefficient is such that the larger the dielectric constant, the larger the value of the temperature coefficient, that is, the smaller the value of the temperature coefficient, the smaller the dielectric constant. Met. Therefore, with the conventional composition, a high dielectric constant could not be obtained when the value of the temperature coefficient was small.

Recently, as a temperature compensating porcelain capacitor used in an IFT (intermediate frequency transformer) circuit of a color television or the like, a capacitor having a particularly small temperature coefficient, a large capacity and a small dielectric loss angle at high frequencies has been demanded. In order to obtain a capacitor with a small temperature coefficient and a large capacity in this way, for example, a CaTiO ₃ -La ₂ O ₃ 2TiO ₂ -MgTiO ₃ -based material is used.
There was no other way than reducing the thickness.

[Problems to be solved by the invention]

However, reducing the thickness causes a decrease in withstand voltage and is an unstable factor in reliability. Also,
Conventionally, CaTiO ₃ has a high dielectric constant ε of 160, but has a drawback that the temperature coefficient is large at −1600 × 10 ⁻⁶ / ° C. For example, Bi ₂ O ₃ · 2TiO ₂ , La ₂ O ₃ · 2TiO _{3 has a} drawback. Addition of such components as the above results in a low temperature coefficient and a relatively high dielectric constant, but the dielectric loss angle at high frequencies is large, and Bi
_{Due to} problems such as evaporation of ₂ O ₃ , the sintered body becomes porous and the insulation resistance (IR) deteriorates. In addition to manufacturing technology, bending and warpage of the sintered body occurred, which was kept in mass productivity.

The present invention has been improved by focusing on these above-mentioned drawbacks, effectively eliminating the drawbacks while effectively utilizing the characteristics of the material, and having a high dielectric constant ε and a temperature coefficient of dielectric constant of − The present invention aims to provide a porcelain composition for temperature compensation, which has a relatively small value of 980 to −720 × 10 ⁻⁶ / ° C. and a high Q.

[Means for solving problems]

In view of the above-mentioned demand, the present inventor has conducted diligent research, and as a result, the main component CaTiO ₃ is 92 to 75 mol% and the SrO.Nb ₂ O ₅ is 8 to 25 mol%, and CaO 21.65 to 33.37 wt% TiO 2 ₂ 30.84 to 47.53 wt% SrO 5.36 to 13.33 wt% Nb ₂ O ₅ 13.75 to 34.19 wt% Ca with MnO added to 0.20 wt% of the composition 100
In which it has reached the present invention found that can prevent reduction of the time of firing by adding the and MnO two-component temperature compensation for the high dielectric constant ceramic composition TiO-SrO · Nb ₂ O ₅ is obtained .

〔Example〕

Calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), titanium oxide (TiO ₂ ), and niobium oxide (Nb ₂ O ₅ ) were used as starting materials, and they were mixed at the composition ratio shown in Table 1 to produce CaCO ₃
And TiO ₂ and SrCO ₃ and Nb ₂ O ₅ were mixed in equimolar amounts, wet-mixed in a porcelain pot mill for 18 hours, dehydrated and dried, and then calcinated at 1100 ° C to 1200 ° C for 2 hours to chemically react. Was done. After roughly pulverizing the reaction product, wet pulverization is again performed for 20 hours using a pot mill. Separately, manganese oxide (MnO) pulverized is added to the above-mentioned pulverized mixture of base materials in an appropriate amount as shown in Table 1, and pulverized by a pot mill. After dehydrating and drying this mixture, a binder was added to form a disc-shaped molded product with a diameter of 16.5 mm and a thickness of 0.6 mm at a molding pressure of about 3 ton / cm ² , and this was molded in the temperature range of 1200 ° C to 1240 ° C. It was fired for 2 hours. A glass frit-containing silver paste was baked on the thus obtained porcelain body to form an electrode.

It is more effective to add a rare earth compound or the like as a mineralizer to improve the sinterability.

Table 1 shows the results of measuring various electrical characteristics of the samples thus manufactured.

Here, the dielectric constant εs was measured at 1 MHz and Q was also measured at 1 MHz. As the measurement conditions, a room temperature of 20 ° C., a Q meter (4340A) and an IR meter (4329A) made by YEW, a capacitance bridge MODEL74D made by Bunton as a temperature coefficient, and EW-102 made by Electropto as a thermostat were used. The temperature coefficient is the dielectric constant value of 20 ℃, 85
It was measured at each temperature of ° C. Here, the temperature coefficient was calculated by the following equation.

However, T / C: Temperature coefficient C _{85 ℃} : Capacitance value at temperature 85 ℃ (PF) C _{20 ℃} : Capacitance value at temperature 20 ℃ (PF) T _{85 ℃} : Measurement temperature T _{20 ℃} ： Measurement temperature As is clear from Table 1, when CaTiO ₃ exceeds 92 mol%, the temperature coefficient becomes large, and when it is less than 75 mol%, Q becomes low. Further, when SrO.Nb ₂ O ₅ exceeds 25 mol%, Q remarkably decreases, and when it is less than 8.0 mol%, the temperature coefficient becomes large.
Thus, the samples No. 6 to No. 9 in Table 1 are most effective, and the samples No. 4 to No. 11 can be put to practical use.

[Advantages of the Invention] The present invention is a high-dielectric-constant ceramic composition for temperature compensation, which comprises two components of CaTiO ₃ —SrO · Nb ₂ O ₅ and has a high dielectric constant and a temperature coefficient of dielectric constant of −980 to −720. It shows a relatively small value of × 10 ^-6 / ° C, has a large Q, does not deteriorate the insulation resistance IR, and is a stable industrial product with no bending or warpage of the sintered body in the manufacturing process. Mass production has become possible.

Claims (1)

[Claims] 1. A main component CaTiO ₃ is 92 to 75 mol%, and SrO.Nb ₂ O ₅
8 to 25 mol% CaO 21.65 to 33.37 wt% TiO ₂ 30.84 to 47.53 wt% SrO 5.36 to 13.33 wt% Nb ₂ O ₅ 13.75 to 34.19 wt% MnO to 0.20 wt% for 100 compositions. %, A high dielectric constant porcelain composition for temperature compensation of a CaTiO-SrO.Nb ₂ O ₅ binary component.