JP2920688B2 - Non-reducing dielectric porcelain composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reducing dielectric ceramic composition, and more particularly to a non-reducing dielectric ceramic composition suitable as a dielectric material for a multilayer capacitor having a base metal such as nickel as an internal electrode. The present invention relates to a conductive dielectric ceramic composition.

(Prior Art) A conventional dielectric porcelain material has the property of being reduced when baking under a neutral or reducing low oxygen partial pressure, and becoming a semiconductor. Therefore, as a material of the internal electrode, the dielectric ceramic material does not melt at the sintering temperature, and is not oxidized even when fired under a high oxygen partial pressure that does not turn the dielectric ceramic material into a semiconductor, such as palladium and platinum. Precious metals must be used, which has been a major obstacle to reducing the cost of the manufactured multilayer capacitor.

Therefore, in order to solve the above problem, it has been desired to use an inexpensive base metal such as nickel as a material for the internal electrodes. However, when such a base metal is used as a material for an internal electrode and fired under conventional conditions, the electrode material is oxidized and does not function as an electrode. Therefore, in order to use such a base metal as a material for an internal electrode, it does not turn into a semiconductor even when fired in a neutral or reducing atmosphere having a low oxygen partial pressure, and has a sufficient insulating property as a dielectric material for a capacitor. There is a need for a dielectric porcelain material having resistance and excellent dielectric properties.
The composition of BaTiO ₃ -CaZrO ₃ -MnO-MgO system 62-256422 Patent Publication, BaTiO ₃ in JP-B 61-14611 - (Mg, Zn, Sr , C
a) O—B ₂ O ₃ —SiO ₂ based compositions have each been proposed.

(Problems to be Solved by the Invention) However, in the non-reducing dielectric ceramic composition disclosed in Japanese Patent Application Laid-Open No. 62-256422, CaZrO ₃ and CaTiO ₃ generated in the firing step are secondary with Mn and the like. There is a risk that the formation of a phase is likely to reduce the reliability at high temperatures.

Further, in the composition disclosed in JP-B-61-14611, the dielectric constant of the obtained dielectric is 2000 to 2800, and the dielectric constant of a conventional porcelain composition using a noble metal such as palladium. Inferior to 3000-3500. Therefore, if this composition is directly replaced with a conventional material for cost reduction, it is disadvantageous in terms of increasing the size and the capacity, and the problem remains.

Further, in the dielectric obtained from the composition disclosed in Japanese Patent Publication No. 61-14611, the temperature change rate of the dielectric constant is -25 ° C to + 85 ° C based on the capacitance value of 20 ° C.
Within the range of ± 10%, but at temperatures higher than + 85 ° C, it greatly exceeds 10%, and there is a drawback that the X7R characteristic specified in the EIA standard is greatly deviated.

Therefore, a main object of the present invention is that even under a low oxygen partial pressure, the structure does not become a semiconductor and can be fired, and the dielectric constant is 3000 or more, and the logarithmic value of the insulation resistance value (logIR) is 11.0.
As described above, when the temperature characteristic of the dielectric constant is based on the capacitance value of 25 ° C., ± 15 ° C. over a wide range of −55 ° C. to 125 ° C.
It is an object of the present invention to provide a non-reducible dielectric porcelain composition capable of obtaining a dielectric material satisfying the range of at most%.

(Means for Solving the Problems) The present invention provides BaTiO ₃ having an alkali metal oxide content of 0.04% by weight or less as an impurity, Tb ₂ O ₃ , Dy ₂ O ₃ ,
Ho ₂ O _3, Er ₂ at least one rare earth oxide selected from among O ₃ (Re ₂ O ₃₎ and Co ₂ O ₃ and as a main component, the mixing ratio, BaTiO ₃ is 88.0 to 99.4 Mol%, Re ₂ O ₃ is 0.3 to 6.0 mol%, and Co ₂ O ₃ is 0.3 to 6.0 mol%.
It is a non-reducing dielectric ceramic composition containing 0.2 to 4.0 mol% of BaO and 0.2 to 3.0 mol% of MnO as subcomponents with respect to mol%.

In addition, Y ₂ O ₃ may be further contained as a minor component in an amount of 3 mol% or less based on 100 mol% of the main component.

In the present invention, the reason why the composition ranges of the main component and the subcomponent are limited as described above will be described below.

 First, the reasons for limiting the composition range of the main component will be described.

The reason why the composition ratio of BaTiO ₃ is set to 88.0 to 99.4 mol% is that when the composition ratio is less than 88.0 mol%, the composition ratio of rare earth oxide and Co ₂ O ₃ increases, so that the insulation resistance value and the dielectric Rate decreases, and if it exceeds 99.4 mol%,
This is because there is no effect of the addition of the rare earth oxide and Co ₂ O ₃ , and the rate of temperature change of the capacity in the high temperature part (near the Curie point) largely deviates to the positive side. The reason why the content of the alkali metal oxide in BaTiO ₃ is set to 0.04% by weight or less is that if the content exceeds this range, the dielectric constant is reduced.

 Next, the reasons for limiting the composition range of the accessory component will be described.

BaO is added to correct the molar ratio of the main component Ba and Ti, but the amount of addition is 0.2 to 4.0 mol% if the addition amount is less than 0.2 mol%. This is because the structure becomes a semiconductor in the inside and the insulation resistance value is remarkably reduced. Conversely, when the added amount exceeds 4.0 mol%, the sinterability decreases.

MnO is added to prevent reduction. However, the addition amount of 0.2 to 3.0 mol% is not effective in improving the reduction resistance of the tissue if the addition amount is less than 0.2 mol%. This is because a remarkable decrease in the resistance value is caused, and if added in excess of 3.0 mol%, the insulation resistance value, particularly the resistance value at high temperatures, is reduced.

Y ₂ O ₃ is added as needed to improve the temperature characteristics of the dielectric constant more flatly.
The reason why the content is set to 3.0 mol% or less is that if added in excess of this, the sinterability is remarkably deteriorated.

(Effects of the Invention) According to the present invention, even when fired at a temperature of 1300 to 1360 ° C in a neutral or reducing atmosphere, the structure is not reduced to a semiconductor, and a logarithmic value (logIR) of 11.0 or more is obtained. X7R, which has a high insulation resistance value, a high dielectric constant of 3000 or more, and a temperature change rate of the capacitance specified by EIA
It is possible to obtain a non-reducible dielectric porcelain composition capable of obtaining a dielectric satisfying the characteristics.

When the non-reducing dielectric ceramic composition according to the present invention is used, for example, as a dielectric material of a multilayer ceramic capacitor, it becomes possible to use a base metal represented by nickel or the like as an internal electrode, which has been conventionally used. Compared with a laminated ceramic capacitor using a noble metal such as palladium as an internal electrode, it is possible to greatly reduce costs without deteriorating characteristics.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments.

(Example) First, as raw materials, BaTiO ₃ , B having different impurity contents were used.
BaCO ₃ , rare earth oxide, to correct the molar ratio of a and Ti,
Cos ₂ O ₃ , MnO and Y ₂ O ₃ were prepared and weighed to have the composition ratios shown in Table 1 to obtain a weighed material. After adding 5% by weight of a vinyl acetate-based binder to the weighed material, the mixture was sufficiently wet-mixed and pulverized with a ball mill using PSZ balls to obtain a mixture. Next, after the dispersion medium in the mixture was evaporated and dried, a powder was obtained through a sizing process. The obtained powder was press-molded at a pressure of ² ton / cm ² into a disk having a diameter of 10 mm and a thickness of 1 mm to obtain a compact.

After holding the compact in air at 400 ° C. for 3 hours to remove the binder, the compact was heated at a temperature shown in Table 2 in a reducing atmosphere gas stream having a H ₂ / N ₂ volume ratio of 3/100. It was fired for 2 hours to obtain porcelain.

By coating and baking an Ag paste on both sides of the obtained porcelain, an electrode is formed as a capacitor, and the dielectric constant ε at room temperature, the dielectric loss tanδ and the insulation resistance value IR, and the temperature change rate TCC of the capacitance are determined. It was measured. The results are shown in Table 2.

Table 2 shows the dielectric constant and dielectric loss.
The results (ε ₂₅ and tan δ) measured under the conditions of a temperature of 25 ° C, a frequency of 1 kHz, and an AC voltage of 1 V are shown. The insulation resistance value is the result of a measurement performed at a temperature of 25 ° C and a DC voltage of 500 V for 2 minutes in advance. Is shown as a logarithmic value (logIR ₂₅ ), and the rate of temperature change of the capacitance is the rate of change of the respective capacitance values at −55 ° C. and 125 ° C. based on the capacitance value (C ₂₅ ) at ₂₅ ° C. (−55 ° C .: ΔC ₋₅₅ / C ₂₅ and + 125 ° C .: ΔC ₊₁₂₅ / C ₂₅ ) and the absolute value of the value at which the capacitance temperature change rate is the maximum between −55 ° C. and + 125 ° C., the so-called maximum change rate (Cmax: | ΔC / C ₂₅ | max).

From the results in Table 2, it is clear that the samples within the scope of the present invention can obtain excellent characteristics in the dielectric constant, the dielectric loss, the insulation resistance value, and the temperature change rate of the capacitance.

The results shown in Table 2 are obtained for single-plate capacitors, but the same results are obtained for multilayer capacitors obtained by forming the same composition into sheets and performing chip processing. .

Claims (2)

(57) [Claims] (1) BaTiO ₃ having an alkali metal oxide content of 0.04% by weight or less as an impurity, Tb ₂ O ₃ , Dy ₂ O ₃ , Ho
_At least one rare earth oxide (Re ₂ O ₃ ) selected from ₂ O ₃ and Er ₂ O ₃ and Co ₂ O ₃ are the main components, and the compounding ratio is such that BaTiO ₃ is 88.0 to 99.4 mol. %, Re ₂ O ₃ is 0.3 to 6.0 mol%, and Co ₂ O ₃ is 0.3 to 6.0 mol%. Based on 100 mol% of the main component, 0.2 to 4.0 mol% of BaO is added as an auxiliary component, and A non-reducing dielectric ceramic composition containing 0.2 to 3.0 mol% of MnO. 2. The method according to claim 1, further comprising:
_2. The non-reducing dielectric ceramic composition according to claim 1, wherein the composition contains 3 mol% or less of Y ₂ O ₃ as an auxiliary component.