JPH0230652A - Reduction inhibitor for dielectric ceramics - Google Patents

Abstract

PURPOSE:To prevent insulation resistance of a lead oxide-based compound oxide dielectric material from deteriorating in calcination in a reducing atmosphere by providing a reduction inhibitor for adding to the above-mentioned dielectric material with a specific composition consisting of respective oxides of Li, an alkaline earth metal, B and Si. CONSTITUTION:The subject reduction inhibitor consists of a composition expressed by the general formula a(LiO1/2+RO)-(1-a)(BO1/2+SiO2) (0.01<=a<=0.80 molar ratio; R is one or more of Mg, Ca, Sr and Ba). If the (LiO1/2+RO) is <0.01 molar ratio or exceeds 0.80 molar ratio in the above- mentioned inhibitor, insulation resistance of a lead oxide-based compound oxide dielectric material is <10<10>OMEGAcm and nonreducing properties cannot be realized. Furthermore, the amount of the inhibitor added to the dielectric material which is the principal component varies with the dielectric material which is the principal component, but is preferably 0.05-25.0wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a reduction inhibitor, particularly to a reduction inhibitor for dielectric ceramics containing lead oxide as a component.

<Prior art and its problems> Lead oxide-based dielectric materials have a relatively high dielectric constant;
It is widely used because it can be fired at low temperatures. ′ On the other hand, when manufacturing a multilayer capacitor using lead oxide dielectric material, internal electrodes are interposed between each dielectric material layer, but lead oxide dielectric material is not used in a reducing atmosphere. Firing generally impairs the insulating properties, so
As the material for the internal electrodes, Ag/Pd-based noble metals are used, which are stable even when fired in an oxidizing atmosphere.

However, Ag/Pd-based materials are expensive and have drawbacks such as deterioration of characteristics due to Ag migration and low conductivity.

<Object of the Invention> Therefore, the present invention provides a reduction inhibitor that can be added to a lead oxide-based composite oxide dielectric material to prevent loss of insulation resistance when fired in a reducing atmosphere. The purpose is to

<Means for Solving the Problems> In order to achieve the above object, the present invention provides the general formula %) [However, 0. O1≦a≦0.80 (molar ratio), R is M
The present invention provides a reduction inhibitor for lead oxide-based composite oxide dielectric ceramics, which is composed of a small amount (all one kind) of the following: (g) Ca%Sr%Ba.

Effect> The reduction inhibitor consisting of these components is added in advance to the main components at a predetermined ratio when sintering the main dielectric material, mixed and formed into a compact, and then subjected to the firing process. brought about.

In this case, the above-mentioned reduction inhibitors may be added individually to the main components, but in addition, the reduction inhibitor may be added in advance, and this may be heat-treated as a powder or heat-treated at a higher temperature and melted. However, it may be crushed and vitrified and then added to and mixed with the main component.

The reason why the reduction inhibitor according to the present invention is limited to the above-mentioned composition range is as follows.

That is, when Li0v+RO is less than o, oi (molar ratio) or exceeds 0.80 (molar ratio), the insulation resistance of the lead oxide-based composite oxide dielectric material to which Li0v+RO is added is 1010Ω.
This is because non-reducibility cannot be achieved if the thickness is less than cm.

The proportion of this reduction inhibitor added to the dielectric material, which is the main component, varies depending on the dielectric material, which is the main component.
A range of 0.05 to 25.0% by weight is suitable. This means that if it is less than 0.05% by weight, non-reduction is not achieved;
This is because if the content exceeds 5.0% by weight, the dielectric properties will be significantly impaired.

<Example> Hereinafter, this invention will be explained in detail with reference to Examples.

72 P b (Mg 4 Nb%) Os 25
Pb (Z n 4 Nby, ) Oa-3PbT
PbaO4, so as to have a composition of i0m (molar ratio)
MgC01, Nbi On, Ti0g, and ZnO were weighed, mixed in a ball mill for 12 hours, and then evaporated to dryness to obtain a mixed powder.

The obtained powder was fired at 800° C. for 2 hours and then coarsely ground to pass through a 200 mesh sieve to prepare a lead oxide dielectric powder.

In addition, LiC0, MgC so as to have the composition shown in Table 1
O5, CaCO5% 5rCOi, BaC0a, B
ias and Sin.

Weigh the powder and put it into an aluminum crucible.
The mixture was left at a temperature of 200° C. for 1 hour, rapidly cooled to vitrify, and then ground to pass through a 200-mesh sieve to prepare a reduction inhibitor.

Next, a reduction inhibitor was added to the lead oxide-based composite oxide dielectric material in the proportions shown in Table 1, a polyvinyl butyral-based binder and an organic solvent were added, and the mixture was heated in a ball mill 24 hours a day. Mixed.

The slurry thus obtained was formed into a green sheet with a thickness of 50 um by a doctor blade method.

A Cu electrode paste was printed on the obtained green sheet by a screen printing method, and after drying, they were stacked to form opposing electrodes and integrated by thermocompression bonding.

Individual capacitor units were cut out from this laminated block using a blade.

Cu electrode paste was applied to the end face of the cut out unit to form an external electrode.

The green unit thus obtained was placed in an electric furnace adjusted to a reducing atmosphere using a mixed gas of N2, N2 and H,0, and fired at 1000°C for 3 hours.

The dimensions of the chip-type multilayer capacitors produced in this example are as specified in each method.

External dimensions 2 Width 4.8 mm, length 5.6
mm Thickness: 1.2 mm Effective dielectric layer thickness (t): 32 μm Effective number of dielectric layers (N): 17 - Counter electrode area per layer (S): 21.5
In addition, the capacitance was measured using an automatic bridge at I KHz and IV, and the dielectric constant (ε) was determined using the following formula.

t,=(113XCXt)/(SXN)=8.
3 x 10-''X C Insulation resistance was measured using a high insulation meter after applying 50V for 2 minutes.

The above results are shown in Table 1.

From the above table, L L Oy2+R, which is a component of the reduction inhibitor
O is 1 mol% (0 in the molar ratio stated in the claims, O
) or less than 80 mol% (also equivalent to 0.8
(equivalent to 0), the insulation resistance becomes IQIOΩCm
It can be seen that non-reducibility is not achieved.

Furthermore, even if the proportion of this reduction inhibitor added to the dielectric material, which is the main component, is less than 0.05% by weight, the insulation resistance will be 101%.
Less than 0 Ωcm, non-reducibility was not achieved, and on the other hand, 25
．． It can be seen that when it exceeds 0% by weight, the dielectric constant becomes less than 4000 and the dielectric properties are significantly impaired.

In addition, in the above-mentioned example, Pb (Mgy, Nb-/
, ) Os −P b (Zn, hNb%) O
Although an example has been described in which the reduction inhibitor for dielectric ceramics of the present invention is added to a dielectric ceramic material containing lead oxide made of x PbTiOs, other dielectric ceramic materials containing lead oxide as shown in Table 2 can also be used. By adding the reduction inhibitor for dielectric ceramics of the present invention to the material, a decrease in insulation resistance can be prevented even if the material is fired in a reducing atmosphere.

On the other hand, in the case where no reduction inhibitor was added, the insulation properties were impaired and the dielectric properties were significantly impaired.

Of course, the reduction inhibitor for dielectric ceramics of the present invention is not limited to the above-mentioned dielectric ceramics containing lead oxide, but is also useful for other dielectric ceramics containing lead oxide.

<Effects of the Invention> As detailed above, by adding the reduction inhibitor according to the present invention to a lead oxide-based composite oxide dielectric material,
This makes it possible to prevent insulation resistance from being impaired when firing in a reducing atmosphere.

Claims (1)

[Claims] General formula a(LiO_1_/_2+RO)-(1-a)(BO_
1_/_2+SiO_2) [However, 0.01≦a≦0.
80 (molar ratio), R is at least one of Mg, Ca, Sr, and Ba] A reduction inhibitor for lead oxide-based composite oxide dielectric ceramics