JPH0510763B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a dielectric ceramic composition, particularly to a dielectric ceramic composition for a capacitor. Conventional Structure and Problems Barium titanate-based materials are widely used as materials for making dielectric ceramic compositions with high dielectric constants for ceramic capacitors. The dielectric constant of conventional dielectric ceramic compositions using this type of material is closely related to its temperature characteristics, and the JIS
A porcelain composition that satisfies the Y class F characteristics specified in the standard (temperature change in permittivity within the temperature range of -25°C to 85°C is within +30% to -80% based on the value at 20°C)
Approximately 10000, Y class D characteristics (+20% to - under the above conditions)
30% or less) is about 4000, and Y class B characteristics (within ±10% under the above conditions) is about 1000. Dielectric ceramic compositions using such barium titanate-based materials have low dielectric loss tan δ and are excellent in other properties such as life characteristics.
It requires a fairly high temperature of 1400℃. Therefore, when making a ceramic capacitor from a composition made of barium titanate-based materials, expensive platinum or palladium-based electrodes are required as internal electrodes. On the other hand, Pb(Fe _1/2 Nb 1/2 ) O ₃ , Pb(Fe 1/2 Nb _1/2 ) O 3 ,
Pb(Fe2 _{/3W1 / 3} )O3,Pb(Mg1 _{/ 3N2/ 3} )O3,Pb
Dielectric compositions in which complex oxides such as (Zn _1/3 Nb _2/3 )O ₃ are combined are known. A dielectric composition made of this type of material is not known to have the above-mentioned Y-class B characteristics, which require a large change in dielectric constant with temperature and a small rate of change with temperature. Furthermore, dielectric compositions of this type that exhibit a large relative dielectric constant have a large particle size after firing and therefore have low mechanical strength, which may cause various practical problems. Therefore, the firing temperature is low and there is no need to use platinum-based or palladium-based electrode materials as electrodes.
It is clear that if a dielectric ceramic composition with excellent temperature characteristics and mechanical strength could be obtained, it would have great industrial value. Purpose of the invention The present invention has a low firing temperature of 900 to 1100°C, and has Y class D characteristics or Y class B characteristics specified by JIS standards.
The object of the present invention is to provide a dielectric ceramic composition for a capacitor, which has a characteristic temperature change rate and has a dielectric constant equivalent to that of the barium titanate-based dielectric ceramic composition. Structure of the Invention The dielectric ceramic composition for capacitors of the present invention includes:
Pb(Fe2 _{/3W1 /3} ) _O3 ,Pb(Mg1 _{/ 2W1/2} ) _O3 ,Pb
(Zn _1/2 W _1/2 ) O ₃ , and at least one tungsten-containing compound selected from the group consisting of Pb (Ni _1/2 W _1/2 ) O ₃ and Pb (Fe _1/2 Nb _{1 /2} ) O ₃ , Pb (Zn _1/3
Nb _2/3 ) O ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni _1/3
At least one selected from the group consisting of Nb _2/3 ) O ₃
The first component is 50 to 90 mol % of a solid solution containing at least one niobium-containing compound, and the second component is 50 to 10 mol % of a solid solution containing BaTiO ₃ as a main component. In the dielectric ceramic composition according to the present invention, the dielectric loss tan δ can be improved by adding MnO ₂ , so it is preferable to add MnO 2 . However, the addition of MnO ₂ is about 0.2% by weight and the tanδ is 1%.
However, if it exceeds 1% by weight, tan δ becomes large again, so it is preferable that the amount of MnO ₂ added is 1% by weight or less. As the solid solution containing BaTiO ₃ as the main component, which is the second component, a solid solution containing Sr, Zr, and Sn can also be used. For example, Ba _1-x Sr _x TiO ₃ (x is 0<
x≦0.2), BaTi _1-y Zr _y O ₃ (y is 0<y≦
0.15) and BaTi _1-z Sn _z O ₃ (z is 0<z≦
0.1) can be used. If the first component does not contain a tungsten-containing component, the firing temperature of the dielectric ceramic composition formed will exceed 1100° C., which is not preferable. Further, if the niobium-containing component is not contained, the dielectric constant becomes small and a dielectric constant equivalent to that of barium titanate-based dielectric ceramics cannot be obtained, which is not preferable. If the first component is less than 50 mol% and the second component is more than 50 mol%, the firing temperature will exceed 1100°C, which is not preferred. Furthermore, if the first component exceeds 90 mol%, and therefore the second component is less than 10 mol%, 85
This is not preferable because the change in dielectric constant with respect to °C becomes large. Furthermore, if the content of BaTiO ₃ in the second component is low, for example, if the Sr, Zr, and Sn components are increased, the rate of change in dielectric constant with temperature increases, which is not preferable. Any conventionally known method can be used to produce the dielectric ceramic composition of the present invention. Description of Examples The present invention will be described below with reference to Examples. Example The first component of each sample shown in Table 1 was chemically pure PbO, Fe ₂ O ₃ , MgO, ZnO, NiO,
WO ₃ and Nb ₂ O ₅ were weighed to have the composition of each first component shown in Table 1. Separately, the second component of each sample shown in Table 1 was chemically pure BaCO ₃ , SrCO ₃ , TiO ₂ ,
ZrO ₂ and SnO ₂ were weighed so as to have the composition of each second component shown in Table 1. Furthermore, the dielectric ceramic composition of this example contained MnO ₃ in the proportions shown in Table 1. Put each of the above ingredients into a polyethylene pot in the composition ratio of each sample, then add pure water and agate cobbles, stir and mix for 15 hours, remove the agate cobbles, dry, and pre-fire at 650-850℃. did. This roasted product was placed in a polyethylene pot again, pure water and agate cobbles were added thereto, and the pot was crushed for 15 hours. After removing the agate cobbles, it was dried. After that, a polyvinyl alcohol aqueous solution was added as a binder to each dried sample.
The samples were pressure-molded into a cylinder with a diameter of 13 mm and a height of 10 mm, and after the binder was incinerated, the samples were placed in a magnesia container and fired at the firing temperatures shown in Table 1. Each of the obtained fired samples was cut to a thickness of 1 mm, and Cr-Au was deposited on both sides to form electrodes in order to measure the dielectric properties of the fired samples.
Relative permittivity, tanδ at 20℃ at 1KHz, 1V/mm electric field
And the temperature change rate of dielectric constant from -25°C to 85°C was measured. These results are shown in Table 1.

【table】

[Table] Those marked with * in Table 1 above are samples outside the scope of the present invention. As is clear from the data in Table 1 above, the dielectric ceramic composition according to the present invention can be fired at a temperature of 1100° C. or lower, and therefore it is possible to use inexpensive internal electrode materials such as silver. In addition, the dielectric constant is equivalent to that made from conventional materials, and -
In the temperature range of 25℃ to 85℃, the dielectric constant range is within -30% based on the value at 20℃, all of them satisfy the Y class D characteristics specified in the JIS standard, and ±
It can be seen that products satisfying the Y-class B characteristics within 10% can also be obtained. From the data of the sample outside the scope of the present invention in Table 1 above
Pb(Fe2 _{/3W1 /3} ) _O3 ,Pb(Mg1 _{/ 2W1/2} ) _O3 ,Pb
(Zn _1/2 W _1/2 ) O ₃ and Pb (Ni _1/2 W _1/2 ) O ₃ , that is, materials that do not contain tungsten-containing components in the first component, have a firing temperature of 1100°C or higher. (See sample number 12). Also, if the second component, whose main component is BaTiO ₃ , exceeds 50 mol%, the firing temperature will also change in this case.
The temperature exceeds 1100℃ (see sample numbers 15, 21, and 26). In addition, in the second component, Sr, Zr, and Sn are each 0.2,
If it exceeds 0.15 or 0.1, the temperature change rate of dielectric constant will be -30
% or more (see sample numbers 30, 33, and 36). Effects of the Invention As described above, the dielectric ceramic composition according to the present invention has excellent temperature characteristics and the firing temperature can be lowered, so that a multilayer ceramic capacitor using an inexpensive internal electrode material such as silver can be produced. can do.

Claims (1)

[Claims] 1 Pb (Fe _2/3 W _1/3 ) O ₃ , Pb (Mg _1/2 W _1/2 ) O ₃ , Pb
(Zn _1/2 W _1/2 ) O ₃ , and at least one tungsten-containing compound selected from the group consisting of Pb (Ni _1/2 W _1/2 ) O ₃ and Pb (Fe _1/2 Nb _{1 /2} ) O ₃ , Pb (Zn _1/3
Nb _2/3 ) O ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni _1/3
At least one selected from the group consisting of Nb _2/3 ) O ₃
A capacitor comprising 50 to 90 mol% of a first component which is a solid solution containing at least one niobium-containing compound, and 50 to 10 mol% of a second component which is a solid solution containing _BaTiO3 as a main component. Dielectric ceramic composition. 2 The solid solution mainly composed of BaTiO ₃ as the second component is
The dielectric ceramic composition for a capacitor according to claim 1, which is a solid solution of 100% BaTiO ₃ . 3 The solid solution mainly composed of BaTiO ₃ as the second component is
The dielectric ceramic composition for a capacitor according to claim 1, which is a solid solution represented by Ba _1-x Sr _x TiO ₃ (in the formula, x satisfies 0<x≦0.2). 4 The solid solution mainly composed of BaTiO ₃ as the second component is
The dielectric ceramic composition for capacitors according to claim 1, which is a solid solution represented by BaTi _1-y Zr _y O ₃ (where y is 0<y≦0.15). 5 The solid solution mainly composed of BaTiO ₃ as the second component is
The dielectric ceramic composition for a capacitor according to claim 1, which is a solid solution represented by BaTi _1-z Sn _z O ₃ (where z is 0<z≦0.1). 6. The dielectric ceramic composition for a capacitor according to any one of claims 1 to 5, further containing 1% by weight or less of MnO ₂ .