JPS58178904A - High dielectric constant porcelain dielectric composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high permittivity porcelain dielectric composition, particularly a porcelain dielectric composition suitable for a laminated capacitor, which has a relatively low temperature change rate while ensuring a high dielectric constant. The present invention relates to a dielectric composition.

Conventionally, porcelain dielectrics with flat permittivity-temperature characteristics have been mainly composed of barium titanate (BaTi03) and bismuth oxide (B1203), in addition to tin oxide (8n02) or titanium oxide ('l''10z). ) or with zirconium oxide (Zr02) added, but in both cases the rate of change in dielectric constant with temperature is small, for example within ±40%, in the temperature range of -80°C to 185°C. The dielectric constant is low, for example, 4,000 or less, and in the case of a dielectric constant of 4,000 or more, the temperature change rate of the dielectric constant must be large in the above temperature range.

On the other hand, as a porcelain electrical composition that solves this problem,
BaTiO3 and B12O3, Nb2O5 and CeO
Japanese Patent Publication No. 55-21402 discloses an attempt to add 2' or L~03 and thereby achieve a high dielectric constant with a small rate of change in dielectric constant with temperature. However, in such compositions,
The B12O3 contained in the composition may be evaporated if high firing temperatures are employed in making multilayer capacitors, thereby creating a problem of damaging the electrodes, thus creating problems in compositions containing components such as B12 (J3 The material was unsuitable for use in multilayer capacitors.

The present invention has been made against the background of the above circumstances, and its purpose is to have improved dielectric constant temperature change characteristics, high electric reading rate, and suitable for use in multilayer capacitors. Our goal is to provide a porcelain island electric body.

Therefore, the high permittivity ceramic dielectric composition according to the present invention is made of high purity titanic acid formed from barium carbonate (BaC03) with a purity of 99% or more and titanium oxide (Ti02) with a purity of 99% or more. Barium (BaTi03) is 95-9.
Cobalt i-ide (C0203) accounts for 9%, the balance is 0.05-0.5%, and niobium oxide (C0203) accounts for 0.5-2%.
Nb, 05), more than 0.5% and less than 2% cerium oxide (Ce02), and up to 1.5% titanium oxide (Ti
02) (all percentages are based on weight).

According to the porcelain dielectric composition having the composition according to the present invention, it is possible to obtain a high electric current and a small rate of change in humidity. When using the dielectric constant of °C as a reference, it is possible to easily achieve a dielectric constant of 14,000 or more within ±40% of the temperature change rate of the dielectric constant, and even easily obtain a dielectric constant of 6,000 or more. It is possible.

Moreover, since the porcelain dielectric composition obtained by firing according to the present invention does not contain evaporable components such as BI203 and PbO, even if a high firing temperature is employed, the electrodes will not be damaged. There is no problem at all, and therefore it can be suitably used for multilayer capacitors.

In addition, in the present invention, first, high-purity BaTiO3
It is necessary to incorporate it into the composition at a ratio of 95 to 99% by weight, preferably 96 to 99% by weight. If the ratio is too high or low, the dielectric constant may drop significantly or the dielectric This causes problems such as significant temperature changes in the rate. This A-purity BaTiO3 is different from the conventional B-purity BaTiO3.
BaCO3 with aTiO3 of about 97-98% and 98-9
They are formed using about 9% Ti02ffi, while the purity of each is 99% or more, preferably 99.5%.
% or more of highly purified BaCO3 and TiO2, and only by using such high-purity starting materials can high-purity B a T i 03 be obtained.

Further, O n, 03 and N constituting the composition according to the present invention
b2O5 is a component that flattens the temperature change rate of dielectric constant, co2°03 is 0.05 to 0°5%, preferably 0.09 to 0.4%, and Nb, o is 0゜5
It is necessary to incorporate it in a proportion of ~2%, preferably 0.9-1.5% (both based on weight). In addition,
When CO203 is less than 0.05%, the temperature change rate of the dielectric constant becomes large, and when it is more than 0.5%, the dielectric constant becomes low. Also, when Nb106 is less than 0.5%, a problem of poor sintering occurs, while when it is more than 2%! A problem arises in that the rate of temperature change increases.

Furthermore, although CeO2 in the composition of the present invention has the effect of lowering the firing temperature, if its proportion is too small or too large, it will lead to an increase in the temperature. ! There is a problem that the improvement effect of $ is not fully achieved and the rate of change of dielectric constant with temperature becomes large. Therefore, CeO
The proportion of 2 must be more than 0.5% and less than 2% by weight, preferably 0.50 to 1.27% by weight.

Furthermore, like CeO2, TiO2 contributes to lowering the sintering temperature, but if its proportion is too large, it lowers the dielectric constant9 and increases the net loss (tan δ), so the ratio of TiO2 to 1.5 It is necessary to make the content up to 0.2% to 1.0% by weight, and its effective effect is exhibited. In addition, this T+02 rice can be introduced by combining it with excess 'l' + 02 f Ba C03 when forming the high-purity BaTiO3, and a necessary amount of Tiez can also be introduced separately into the composition. It can also be introduced by blending it with.

Thus, the present invention provides specific BaTiO3 and CQIO
3. At a predetermined ratio of Nb2O5, CeO2, and T10□,
By constructing the porcelain shell, it was possible to exhibit many of the excellent features mentioned above.

Examples will be given below to clarify the present invention in more detail, but it goes without saying that the present invention is not limited in any way by the description of the examples. In addition, all weights and percentages in the examples are shown on a weight basis.

Examples The raw materials for each component were wet-mixed uniformly in a ball mill so that the proportions shown in Table 1 were obtained, and then 900 to 1
After calcining at 000°C for 3 hours to carry out a chemical reaction, the mixture was ground again in a ball mill until the average particle size was about 1 micron. In addition, in order to form the high purity BaTiO3 component, BaCOa with a purity of 99.5% and TiO2 with a purity of 99.9% were used, and were wet mixed together with other components in a ball mill. Ta.

Next, after drying this mixture, a suitable amount of polyvinyl alcohol was added as a binder, and it was molded at a pressure of about 1 ton/C- to form a disc-shaped molded product with a diameter of 161 mm and a thickness of 0.5%. Created.

Furthermore, about 1850
After performing main firing for 3 hours at ~1400°C, fM degrees, the resulting fired product was used as a sample by baking silver electrodes on both sides, and then heated for 3000 hours.
After carrying out a life test of applying plQKV per sample thickness l Ml, each i! The characteristics of the 1-temperature island were measured and the results are shown in Table 2.

As is clear from the results in Tables 1 and 2, the compositions according to the present invention all have a high dielectric constant (G) of 4,000 or more, and even 6,000 or more, and have a small dielectric constant. In addition to having a low tan δ, it also has the property of having a smaller rate of change in temperature than conventional raw material compositions.

On the other hand, from a composition using normal eggplant B a COa and TiO2 as starting materials, which has almost the same composition as Sample No. 3, a dielectric constant (J) of only about 3000 can be obtained. Electricity ratio (ε) of sample depth 3 according to the invention = 5158
It was significantly inferior to that of

Also, Ca2O3, Nb2O5, CeO2 and fTiO
The dielectric constant (t) of the one consisting only of high purity B a T IO2 without containing 21 is 2400. & electric loss (t
an δ) was 8.4, and the rate of change at +85°C and -80°C was -19.8% and -32%, respectively, which was significantly inferior to the composition according to the present invention. . Furthermore, in porcelain obtained from a BaTiO3 raw material composite containing a known ZrO2 shifter, if the temperature change rate of the dielectric constant is kept within ±40%, the dielectric constant can reach a maximum of 455.
(In comparison, it was confirmed that the present invention has a significantly superior effect reaching 6,000 or more, even though only 1 was not obtained.)

Chapter 1 Table

Claims (1)

[Claims] High purity barium titanate formed from barium carbonate with a purity of 99% or more and titanium oxide with a purity of 99% or more accounts for 95 to 99%, and the balance is cobalt oxide of 0.05 to 0.5%; 0.5-2% niobium oxide and 0.5
% but not more than 2% cerium oxide and up to 1.5% titanium oxide.