JPH0778510A - Nonreducing dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a nonreducing dielectric porcelain composition not becoming a semiconductor even baked in a reducing atmosphere, and moreover capable of obtaining a large dielectric constant regardless of a small crystal particle diameter and of miniaturizing a laminated ceramic capacitor through using this composition. CONSTITUTION:The main component of this composition is expressed by the following formula; {Ba1-x-y-zSrxCayRez)-O1+z/2}m (Ti1-o-p-qZroHfpNbq)-O2+q/2, and (x), (y), (z), (o), (p), (q), and (m) satisfy the following relation; 0<x<=0.32, 0<=y<=0.20, 0<z<=0.02, 0<o<=0.24, 0<p<=0.16, 0<q<=0.015, 1.00<=m<=1.03, and 0<z+q<=0.025. When the respective oxides of Mn, Fe, Cr, Co, and Ni are represented by MnO2, Fe2O3. Cr2O3, CoO, and NiO, at least one kind of the respective oxides is to be contained by 0.02-2.0mol to obtain a nonreducing dielectric porcelain composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reducing dielectric porcelain composition, and more particularly to a non-reducing dielectric porcelain composition for use in, for example, laminated ceramic capacitors.

[0002]

2. Description of the Related Art In the process of manufacturing a monolithic ceramic capacitor, first, a sheet-shaped dielectric material is prepared by coating an electrode material for forming internal electrodes on the surface thereof. As the dielectric material, for example, a material containing BaTiO ₃ as a main component is used. A sheet-shaped dielectric material coated with this electrode material is laminated, thermocompression bonded, and the integrated product is fired at 1250 to 1350 ° C. in a natural atmosphere to obtain a dielectric ceramic having internal electrodes. Then, an external electrode that is electrically connected to the internal electrode is printed on the end surface of the dielectric ceramic to obtain a monolithic ceramic capacitor.

Therefore, the material for the internal electrodes must satisfy the following conditions.

(A) Since the dielectric porcelain and the internal electrodes are fired at the same time, the dielectric porcelain must have a melting point higher than the firing temperature.

(B) It should not be oxidized even in an oxidizing high temperature atmosphere and should not react with the dielectric.

Noble metals such as platinum, gold, palladium or alloys thereof have been used as the electrode material satisfying such conditions.

However, while these electrode materials have excellent characteristics, they are expensive. Therefore, the ratio of the electrode material cost to the monolithic ceramic capacitor is 30 to 7
It reached 0%, which was the biggest factor in raising the manufacturing cost.

N having a high melting point other than precious metals
Although there are base metals such as i, Fe, Co, W, and Mo, these base metals are easily oxidized in a high-temperature oxidizing atmosphere and cannot serve as an electrode. Therefore, in order to use these base metals as the internal electrodes of the monolithic ceramic capacitor, it is necessary to fire them together with the dielectric ceramic in a neutral or reducing atmosphere. However, the conventional dielectric ceramic material has a drawback that it is remarkably reduced when it is fired in such a reducing atmosphere and becomes a semiconductor.

In order to overcome such drawbacks, for example, as shown in Japanese Patent Publication No. 57-42588, in a barium titanate solid solution, the barium site / titanium site ratio is set to be more than stoichiometric. The body material was devised. By using such a dielectric material, it is possible to obtain a dielectric ceramic that does not become a semiconductor even when fired in a reducing atmosphere, and it is possible to manufacture a monolithic ceramic capacitor that uses a base metal such as nickel as an internal electrode. Became.

[0010]

With the recent development of electronics, miniaturization of electronic parts has rapidly progressed, and the tendency of miniaturization of monolithic ceramic capacitors has become remarkable. As a method for miniaturizing the monolithic ceramic capacitor, it is generally known to use a material having a large dielectric constant or to thin the dielectric layer. However, a material having a large dielectric constant has a large number of crystal grains, and when the film is a thin film having a thickness of 10 μm or less, the number of crystal grains present in one layer decreases, and reliability decreases.

On the other hand, as disclosed in Japanese Patent Laid-Open No. 61-101459, a solid solution of barium titanate with La, N is used.
There is known a non-reducing dielectric ceramic having a small crystal grain size, to which a rare earth oxide such as d, Sm or Dy is added. By reducing the crystal grain size in this manner, the number of crystal grains present in one layer can be increased, and a decrease in reliability can be prevented.

[0012] However, the material to which the rare earth oxide is added cannot obtain a large dielectric constant and is easily reduced during firing, which is a problem in terms of characteristics.

Therefore, the main object of the present invention is that even if it is fired in a reducing atmosphere, it does not become a semiconductor and, despite its small crystal grain size, a large dielectric constant is obtained. It is an object of the present invention to provide a non-reducing dielectric ceramic composition capable of miniaturizing a monolithic ceramic capacitor.

[0014]

According to the present invention, the main component is the following composition formula: {(Ba _1-xyz Sr _x Ca _y Re _z ).
_{O 1 + z / 2} m} (Ti 1-opq Zr o Hf p Nb q) O
_{2 + q / 2} (where Re is at least one selected from Dy, Ho, Er, Yb and Y), x,
y, z, o, p, q and m are 0 <x ≦ 0.32, 0
≦ y ≦ 0.20, 0 <z ≦ 0.02, 0 <o ≦ 0.2
4, 0 <p ≦ 0.16, 0 <q ≦ 0.015, 1.00
Satisfying the relations of ≦ m ≦ 1.03 and 0 <z + q ≦ 0.025, and Mn, Fe, and C with respect to 100 moles of the main component.
The oxides of r, Co, and Ni were replaced with MnO ₂ , Fe ₂ O ₃ , and C.
When represented as r ₂ O ₃ , CoO, and NiO, the non-reducing dielectric ceramic composition contains 0.02 to 2.0 mol of at least one kind of each oxide.

[0015]

According to the present invention, it is possible to obtain a non-reducing dielectric ceramic composition which is not reduced even when fired in a reducing atmosphere and does not become a semiconductor. Therefore, if a porcelain multilayer capacitor is manufactured using this non-reducing dielectric porcelain composition, a base metal can be used as an electrode material.
Since it can be fired at a relatively low temperature of 300 ° C. or lower, the cost of the monolithic ceramic capacitor can be reduced.

Further, in the porcelain using this non-reducing dielectric ceramic composition, the dielectric constant is 11,000 or more, and despite having such a high dielectric constant, the crystal grain is 3 μm.
It is as small as m or less. Therefore, when a multilayer ceramic capacitor is manufactured, even if the dielectric layer is thinned, the amount of crystal grains existing in the layer does not decrease unlike the conventional multilayer ceramic capacitor. Therefore, it is possible to obtain a highly reliable, small-sized, large-capacity monolithic ceramic capacitor.

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

[0018]

EXAMPLES First, as a raw material, B having a purity of 99.8% or more was used.
aCO ₃ , SrCO ₃ , CaCO ₃ , Dy ₂ O ₃ , Ho
₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Y ₂ O ₃ , Ti
O ₂ , ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , MnO ₂ , F
e ₂ O ₃ , Cr ₂ O ₃ , CoO, and NiO were prepared. These raw materials _{{(Ba 1-xyz Sr x} Ca y Re z) O
_{1 + z / 2} } _m (Ti _1-opq Zr _o Hf _p Nb _q ) O
_Expressed by the composition formula of _{2 + q / 2} , x, y, z, m, o, p, q
Were blended in the proportions shown in Table 1 and Table 2 to obtain blended raw materials. The blended raw materials were wet mixed in a ball mill, pulverized, dried, and calcined in air at 1100 ° C. for 2 hours to obtain a calcined product. The calcined product was crushed by a dry crusher to obtain a crushed product having a particle size of 1 μm or less. Pure water and a vinyl acetate binder were added to this pulverized product, and the mixture was mixed for 16 hours with a ball mill to obtain a mixture.

[0019]

[Table 1]

[0020]

[Table 2]

After this mixture was dry granulated, 2000 k
Molded with a pressure of g / cm ² , diameter 10 mm, thickness 0.5
A disc of mm was obtained. The resulting disk is 50 in air
After heating to 0 ° C. to burn the organic binder, H ₂ —N ₂ having an oxygen partial pressure of 2 × 10 ^{−10 to} 3 × 10 ⁻¹² atm.
-In a reducing atmosphere furnace composed of air gas, firing was performed for 2 hours at the temperatures shown in Tables 3 and 4 to obtain a disk-shaped porcelain.
The surface of the obtained porcelain was magnified 150 with a scanning electron microscope.
Observation was carried out at 0 times and the grain size was measured.

[0022]

[Table 3]

[0023]

[Table 4]

Then, a silver electrode was baked on the main surface of the obtained porcelain at a temperature of 600 ° C. in an N ₂ atmosphere to obtain a measurement sample (capacitor). The rate of change of the dielectric constant (ε) at room temperature, the dielectric loss (tan δ), and the capacitance (C) with respect to temperature changes was measured for the obtained sample. The dielectric constant and the dielectric loss are 25 ° C and 1k.
It was measured under the conditions of Hz and 1 V _rms . Regarding the rate of change of the capacitance with respect to temperature change, the rate of change at −25 ° C. and 85 ° C. (ΔC /
C ₂₀ ) and a value (| ΔC / C ₂₀ | _max ) at which the rate of change is maximum as an absolute value within the range of −25 ° C. to 85 ° C.

Furthermore, by means of an insulation resistance tester, 50
The insulation resistance value was measured after a direct current of 0 V was applied for 2 minutes. The insulation resistance was measured at 25 ° C. and 85 ° C., and the logarithm (logρ) of each volume resistivity was calculated. The results of these measurements are shown in Tables 3 and 4.

Next, the reasons for limiting each composition will be described.

[0027] _{{(Ba 1-xyz Sr x} Ca y Re z) O
_{1 + z / 2} } _m (Ti _1-opq Zr _o Hf _p Nb _q ) O
_{At 2 + q / 2} , when the Sr amount x is 0 as in sample number 1, the dielectric constant is less than 11000 and the dielectric loss is 2.0%.
And the rate of change in capacitance with temperature is large, which is not preferable. On the other hand, as in sample No. 18, the Sr amount x is 0.32
When it exceeds, the dielectric constant is less than 11,000 and the temperature change rate of the capacitance does not satisfy the F characteristic of JIS standard, which is not preferable.

When the Ca content y exceeds 0.20 as in Sample No. 19, the sinterability deteriorates and the dielectric constant decreases, which is not preferable.

Further, when the Re amount z is 0 as in Sample No. 2, the dielectric constant is less than 11000 and the temperature change rate of the capacitance is large, which is not preferable. On the other hand, sample number 20
As described above, when the Re amount z exceeds 0.02, the dielectric loss exceeds 2.0% and the insulation resistance decreases, which is not preferable.

When the Zr amount o is 0 as in Sample No. 3, the dielectric constant is less than 11000 and the rate of change in capacitance with temperature is large, which is not preferable. On the other hand, when the Zr amount o exceeds 0.24 as in Sample No. 22, the sinterability decreases and the dielectric constant becomes less than 11,000, which is not preferable.

Further, as in Sample No. 4, the Hf amount p is 0.
In the case of, the dielectric constant is less than 11000, and the temperature change rate of the capacitance does not satisfy the JIS standard F characteristics, which is not preferable. In addition, as in Sample No. 23, the Hf amount p is 0.16
When it exceeds, the temperature change rate of the capacitance does not satisfy the F characteristic of JIS standard, which is not preferable.

Further, as in Sample No. 5, when the Nb amount q is 0, the dielectric constant is less than 11000 and the crystal grain size is larger than 3 μm, and in the case of a laminated ceramic capacitor, the dielectric layer is thinned. It is not possible and not preferable. on the other hand,
When the Nb amount q exceeds 0.015 as in Sample No. 24, the porcelain is reduced when fired in a reducing atmosphere,
It is not preferable because it becomes a semiconductor and the insulation resistance is significantly reduced.

When the sum z + q of the Re amount z and the Nb amount q exceeds 0.025 as in Sample No. 25, the porcelain is reduced when it is fired in a reducing atmosphere to become a semiconductor, and the insulation resistance is greatly increased. It is not preferable because it decreases.

In addition, like sample No. 6, {(Ba
_{1-xyz Sr x Ca y Re} z) O 1 + z / 2} m (Ti
_When the molar ratio m of _1-opq Zr _o Hf _p Nb _q ) O _{2 + q / 2} is less than 1.00, the porcelain is reduced when fired in a reducing atmosphere, becoming a semiconductor, and the insulation resistance decreases. It is not desirable. On the other hand, as in Sample No. 21, the molar ratio m
Is more than 1.03, the sinterability is extremely deteriorated, which is not preferable.

Further, as in Sample No. 7, MnO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , CoO, Ni as additives were added.
If the amount of O added is less than 0.02 mol, the insulation resistance at 85 ° C. or higher becomes small, and the reliability of long-term use at high temperature is reduced, which is not preferable. On the other hand, if the amount of these additives exceeds 2.0 mol as in Sample No. 26, the dielectric loss increases to more than 2.0% and at the same time the insulation resistance deteriorates, which is not preferable.

On the other hand, when the non-reducing dielectric ceramic composition of the present invention is used, the dielectric constant is as high as 11000 or more, the dielectric loss is 2.0% or less, and the rate of change in capacitance with temperature is It is possible to obtain a dielectric porcelain satisfying the F characteristic standard defined in JIS in the range of -25 ° C to 85 ° C. Furthermore, in this dielectric porcelain, the insulation resistance at 25 ° C. and 85 ° C. is 1 when expressed as the logarithm of the volume resistivity.
It shows a high value of 2 or more. Further, the non-reducing dielectric ceramic composition of the present invention can be sintered at a relatively low firing temperature of 1300 ° C. or less, and has a small particle size of 3 μm or less.

In the above embodiment, the starting material is
BaCO ₃ , CaCO ₃ , TiO ₂ , ZrO ₂ , HfO
_Although oxide powders such as ₂ are used, the oxide powders are not limited to these oxide powders, and powders produced by an alkoxide method, a coprecipitation method, or a hydrothermal synthesis method may be used.
By using these powders, there is a possibility that the characteristics shown in this example will be improved.

In the non-reducing dielectric ceramic composition according to the present invention, the addition of a slight amount of a sintering aid such as silica or oxide glass does not impair the obtained characteristics.

Claims (1)

[Claims] 1. The composition formula {(Ba
_{1-xyz Sr x Ca y Re} z) O 1 + z / 2} m (Ti
_1-opq Zr _o Hf _p Nb _q ) O _{2 + q / 2} (where Re
Is at least one kind selected from Dy, Ho, Er, Yb and Y), and x, y, z, o, p, q and m are 0 <x ≦ 0.32 0 ≦ y ≦ 0 .20 0 <z ≦ 0.02 0 <o ≦ 0.24 0 <p ≦ 0.16 0 <q ≦ 0.015 1.00 ≦ m ≦ 1.03 0 <z + q ≦ 0.025 However, based on 100 moles of the main component, M
The oxides of n, Fe, Cr, Co, and Ni are mixed with MnO ₂ , F.
e ₂ O ₃ , Cr ₂ O ₃ , CoO, NiO,
A non-reducing dielectric ceramic composition containing 0.02 to 2.0 mol of at least one kind of each oxide.