JPS6199207A - High-permeability porcelain 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 (Industrial Application Field) The present invention provides a ceramic composition that can be sintered at a low temperature of about 1200°C, has a small rate of change in dielectric constant over a wide temperature range, has a large dielectric constant, The present invention also relates to an excellent dielectric ceramic composition with low dielectric loss.

(Prior Art) Conventionally, ceramic compositions with a high dielectric constant and a small temperature change in dielectric constant have been prepared by adding Nb, O, -MnO to BaTiO3 (Japanese Patent Publication No. 57-41042), Nb, 0. -C
oO etc. (Electrocomponent)
nt 5science and Tec, 1976, V
ol, 2, P, 241-247), Nb2O5MgO
(Japanese Unexamined Patent Publication No. 48-53297), NbzO
s -MgO-CaTi0t added (Special public interest
7-23366), one to which C0NbzObLaz03 was added (Japanese Patent Application Laid-Open No. 57-88612), and many others (later known).

However, the temperature at which these compositions are sintered is a high temperature of 1350 to 1400°C. Therefore, when using this in multilayer capacitors, it is necessary to use expensive noble metals such as platinum and palladium that can withstand this high sintering temperature as the internal electrode material, which is the biggest cause of cost increase. was. Therefore, in order to manufacture multilayer capacitors at low cost, there is a desire for a porcelain composition that can be sintered at a low temperature of about 1200°C, which allows the use of inexpensive metals mainly composed of silver for the internal electrodes. . 'Currently, BaTi is a porcelain composition that can be sintered at low temperatures.
Compositions in which a bismuth compound is added to O3 are known, but these have drawbacks such as extremely stable performance due to the evaporation of the components during firing (in addition, large dielectric loss in high frequency characteristics). Yes, it is still not satisfactory as a ceramic composition for multilayer capacitors.

In addition, as a composition that does not contain a bismuth compound and can be sintered at a relatively low temperature, BaTrO3 is combined with NdzO, Nb,
Those to which o5SrO□, MnO□, and CoO are added are known (Japanese Unexamined Patent Publication No. 57-92!575). However, the sintering temperature of the composition is 1250°C, and the dielectric loss (tan δ) of the resulting porcelain is as large as 1%.
The characteristics are also not satisfactory.

(Problems to be Solved by the Invention) The present inventors have discovered an object that can be sintered at low temperatures without containing a bismuth compound, has a high dielectric constant, and has a temperature change rate of dielectric constant of B characteristic of JIS special grade Y. Alternatively, with the aim of obtaining a dielectric ceramic composition having a small dielectric loss similar to the X7R characteristic of EIA, the following invention was achieved.

(Means for solving the problem) The specification of JP-A-57-208003 describes that C in the composition
It is stated that eO□ has the effect of lowering the firing temperature. However, in the examples, CeO□ is 0.10~
BaTiOs Coz03 added at 0.29% by weight
The sintering temperature of the NbzOs-CeOz-TiO:+ blend is 1350 to 1400°C, which is not satisfactory in terms of low-temperature sintering.

In addition, Nbzos and F were added to BaTi0:+ so that the molar ratio of NbzOs/MgO was in the range of 2.3 to 4.
A composition in which 0.1 to 0.5% by weight of a rare earth element is added to this is disclosed in Japanese Patent Publication No. 55-19007.
In the examples, the sintering temperature is 1200-1380°C
It is stated that. However, even if the composition of the invention is used,
At 1200°C, sintering was insufficient and the insulation resistance value was low. By increasing the rare earth oxide to 0.5% by weight or more in the composition of the invention, sufficient sintering can be achieved at 1200° C., and the insulation resistance value can also be increased. However, the temperature change rate of the dielectric constant becomes large, and desirable temperature characteristics cannot be obtained.

Therefore, the present inventors conducted extensive research on a composition that maintains low-temperature sinterability, yet has a high dielectric constant, good temperature characteristics, and a low tan δ value, and as a result, they discovered the composition of the present invention. That is, the porcelain composition of the present invention contains 95.20 to 98.58% by weight of barium titanate and 0% by weight of cerium oxide.
．． 52-1.50% by weight, niobium heptaoxide 0.85-3.
00% by weight, 0.05-0.35% by weight of magnesium oxide, and the molar ratio of niobium oxide to magnesium oxide is l:o, in the range of 4 to 1:2.2.

The composition range and composition ratio of the present invention can be sintered at a low temperature of about 1200° C., has a high dielectric constant of about 2000, and has a small temperature change rate of dielectric constant over a wide temperature range.

Even more surprisingly, the dielectric loss (tan δ) is also 0.
．． It is small at 7% or less, which is a significant improvement compared to what has been previously reported.

In the case of multilayer capacitors, compositions with particularly low tan δ are desired, and in this respect as well, the ceramic composition of the present invention has great industrial value.

The barium titanate used in the present invention may be obtained by any production method such as a solid phase method, a liquid phase method, an oxalate method, or an alkoxide method. Average particle size is 0.07~065μ
When using particles with uniform particle size m, a porcelain with a uniform microstructure is obtained, the insulation resistance value becomes even larger, and the variation in the value becomes smaller. In the present invention, oxides such as cerium oxide, niobium oxide, and magnesium oxide can be used as they are, but hydroxides, carbonates, nitrates, oxalates, alkoxides, etc. decompose below the sintering temperature and form oxides. Any one can be used as long as it is suitable. Those having an average particle size of 3 μm or less when converted into oxides can be used more preferably.

The proportion of barium titanate in the porcelain composition of the present invention is 95.20 to 98.58% by weight including BaTrO:+, and if the proportion exceeds 98.58% by weight, sintering is difficult; The temperature change rate of the dielectric constant also increases (becomes 9).
If it is less than 5.20% by weight, the dielectric constant is too small to be practical. The proportion of cerium oxide is 0.52 to 1 as CeO□
．． If the proportion is less than 0.52% by weight, sintering is difficult and the insulation resistance value becomes low. 1.50% by weight
If it exceeds , the rate of change in dielectric constant with temperature increases. The proportion of niobium oxide is 0.85 to 3.00% by weight as NbzOs. If the proportion is less than 0.85% by weight, sintering becomes difficult, and if it exceeds 3.00% by weight, the dielectric constant is small and temperature changes The rate also increases. The proportion of magnesium oxide is M
It is 0.05 to 0.35% by weight as gO, and if the proportion is less than 0.05% by weight, the rate of temperature change will be large;
If it exceeds 35% by weight, the dielectric constant will be low. MgO and Nb2
The molar ratio of O5 is in the range of 0.4 to 2.2, and when the molar ratio is less than 0.4, the dielectric constant is small, and when it exceeds 2.2, the temperature change rate of the dielectric constant is large, and tan δ is also large. Become. Also, the molar ratio of MgO and CeO is 3/4 to 5/4
If it is within this range, the dielectric constant is high and the temperature characteristics are also good, which is preferable.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

As a starting material, the average particle size of SEM particle size is 0.2 to 0.
Niobium oxide, cerium 2 oxide, and gnesium oxide are added to barium titanate having a diameter of 3 μm and a specific surface area of 5 to 8 rd/g in the proportions shown in Table 1, and the pure water number is added and mixed. After drying the mixture, add an appropriate amount of polyvinyl alcohol as a binder and make 'lt/cr
A disc-shaped molded product with a diameter of 15 mm and a thickness of 0.6 mm was produced at a molding pressure of 1. Next, this was sintered at 1200°C for 3 hours. Silver electrodes with a diameter of 10 mm were baked on both end faces of the sintered disk at 740° C., and the electrical properties of each electrode were evaluated. Here, the dielectric constant and dielectric loss (tan δ) were measured at 1 kHz using an LCR meter. The insulation resistance value is a value read when a voltage of 500 V is applied using a high insulation resistance meter. The rate of change in dielectric constant (%) was based on 20°C.

In Table 1, sample floors 1, 2, 3, 9, 10, 11,
17.18 are outside the scope of this invention.

As is clear from Table 1, those within the scope of the present invention are 1
It can be sintered at 200℃, and its porcelain properties have a relative permittivity of 20.
It can be seen that the value is as high as about 00, the rate of change in dielectric constant is small, and the dielectric loss field is small.

(Effects of the Invention) As described below, the following effects were found by zero firing.

1(1) Does not contain bismuth compounds and can be sintered at a low temperature of about 1200″C.

(2) In terms of characteristics, the dielectric constant is high at over 2000,
Moreover, the rate of change due to temperature is small.

(3) Low dielectric loss.

Therefore, the ceramic composition of the present invention has excellent electrical properties and is very advantageous in terms of cost, so it is of great industrial value.

Claims (1)

[Claims] Barium titanate 95.20-98.58% by weight, cerium oxide 0.52-1.50% by weight, niobium oxide 0.8%
5-3.00% by weight, magnesium oxide 0.05-0.
A high dielectric constant ceramic composition containing 35% by weight of niobium oxide and having a molar ratio of niobium oxide to magnesium oxide in the range of 1:0.4 to 1:2.2.