JPH06203634A - Dielectric ceramic and ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic, the dielectric constant and the withstand voltage of which are increased by substituting a part of Ba of BaTiO3 with Ca and Er substituting a part of Ti with Zr and adding a predetermined amount of ZnO or/and NiO thereto. CONSTITUTION:Barium carbonate, calcium carbonate, erbium oxide, titanium oxide and zirconium oxide are mixed by wet-mixing at the ratio by which a basic component expressed by the formula: (0.01<=beta<=0.12; 0.003<=gamma<=0.03; 0.996<=alpha+beta+gamma=k<=1.03; 0.1<=x<=0.2) is obtained. Next, the mixture is dried and then calcined in the atmosphere to manufacture the basic component. Next, ZnO or/and NiO of 0.002 to 0.5 parts by weight are added to the obtained basic component of 100 parts by weight, mixed by wet-mixing and dried to obtain a ceramic material powder. Next, an organic binder is added to the ceramic material powder, then molded and the molded body is baked in the atmosphere to obtain a dielectric ceramic base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic having a high dielectric constant and a single-layer or laminated dielectric ceramic capacitor using the dielectric ceramic.

[0002]

BACKGROUND ART porcelain the BaTiO ₃ as a dielectric ceramic substrate for magnetic capacitor (barium titanate) as a main component, or a portion of Ba (barium) of BaTiO ₃ Ca
It is known to use porcelain in which (calcium) is substituted and Ti (titanium) is partially substituted with Zr (zirconium). The maximum value of the relative permittivity of this type of dielectric ceramic is about 14,000.

[0003]

By the way, it is required to increase the capacity and reliability of the dielectric ceramic capacitor. In order to increase the capacitance, it may be considered to reduce the thickness of the dielectric ceramic layer interposed between the pair of electrodes. However, if the dielectric porcelain layer is made thin, the dielectric strength between the pair of electrodes is lowered. As another method for increasing the capacity, there is a method of using a dielectric ceramic having a high relative dielectric constant and a high withstand voltage. However, in the conventional BaTiO ₃ -based dielectric ceramics, there is a limit in relative permittivity and withstand voltage, and there is a limit in increasing the capacity.

Therefore, an object of the present invention is -25 ° C to +8.
The maximum relative dielectric constant in the range of 5 ° C is 14000 or more, tan δ (dielectric loss) at 20 ° C is 1.5% or less, and the resistivity at 150 ° C is 5 × 10 ⁵ MΩ · cm.
And the average particle size of the crystal particles is 4 μm or less,
Another object of the present invention is to provide a dielectric porcelain free of giant particles and a porcelain capacitor using the same.

[0005]

The present invention for attaining the above-mentioned object is (Ba _α Ca _β Er _γ O _k ) (Ti _1-x Zr _x O ₂ ), where α, β, γ, k , X is 0.01 ≦ β ≦ 0.12 0.003 ≦ γ ≦ 0.03 0.996 ≦ α + β + γ = k ≦ 1.030 0.10 ≦ x ≦ 0.20 100 weight consisting of numerical values The basic ingredients of the part,
The present invention relates to a dielectric porcelain containing 0.002 to 0.500 parts by weight of zinc oxide and an additive component composed of either one or both of nickel oxide. As described in claim 2, the dielectric ceramic of claim 1 can be used as a dielectric ceramic base of a ceramic capacitor.

[0006]

FUNCTION AND EFFECT When the dielectric ceramic has the composition specified in the present invention, the maximum relative dielectric constant ε _max in the range of -25 ° C to + 85 ° C is 14000 or more, and the tan δ at 20 ° C is 1.5.
% Or less, the resistivity ρ at 150 ° C. is 5 × 10 ⁵ MΩ ・
cm or more and the average particle diameter is 4 μm or less. Er (erbium) contained in the porcelain of the present invention contributes to the improvement of withstand voltage and the relative dielectric constant. That is, erbium has a function of reducing the average particle size of the crystal particles forming the dielectric ceramic. Further, erbium has a function of suppressing the generation of abnormal particles (giant particles) having a size of, for example, 10 times or more the average particle size of crystal particles. The dielectric porcelain composed of small crystal particles has a higher dielectric strength and a larger relative dielectric constant than the dielectric porcelain composed of large crystal particles.
Nickel oxide and / or zinc oxide contribute to increase the resistivity and the relative dielectric constant.

[0007]

First Embodiment Next, in the first embodiment of the present invention, the dielectric ceramic capacitor 10 shown in FIG. 1 was produced.
This porcelain capacitor 10 is a disk-shaped dielectric porcelain substrate 1
2 and a pair of electrodes 14 and 1 provided on the pair of main surfaces
It consists of 6 and.

In order to obtain the basic component (Ba _α Ca _β Er _γ O _k ) (Ti _1-x Zr _x O ₂ ) for forming the porcelain substrate 12 of FIG. 1, BaCO ₃ (barium carbonate) and CaCO 3
₃ (calcium carbonate) and Er ₂ O ₃ (erbium oxide)
And TiO ₂ (titanium oxide) and ZrO ₂ (zirconium oxide) are prepared, and α indicating the molar ratio of each atom of the basic component,
Raw material mixtures of 23 kinds of basic components in which β, γ, k, and x were changed as shown in sample Nos. 1 to 23 of Table 1 were prepared. In addition, NiO (nickel oxide) and ZnO as additional components
(Zinc oxide) was prepared as shown in Table 1.

[0009]

[Table 1]

A method of manufacturing the dielectric ceramic capacitor according to Sample No. 1 will be described in detail. The basic components of sample No. 1 are
α is 0.940, β is 0.050, γ is 0.020, k
Is 1.010 and x is 0.190, it can be expressed by the following equation. (Ba _0.94 Ca _0.05 Er _0.02 O _1.01 ) (Ti _0.81 Z _0.19
O ₂ ) BaC in a ratio that satisfies the molar ratio of each atom of this basic component
_{O 3, CaCO 3, Er 2} O 3, were weighed _T i O _2, ZrO _2, to give a mixture of this and the like. Next, this mixture was wet-mixed with a ball mill, dried, and then calcined in the air (oxidizing atmosphere) at 1150 ° C. for 2 hours to obtain a basic component.

Next, 0.180 parts by weight of NiO was added to 100 parts by weight of the basic component, wet mixed and pulverized by a ball mill, and dried at 150 ° C. for 3 hours to obtain a porcelain material powder.

Next, a porcelain material powder to which an organic binder was added was molded by a dry press molding method to obtain a diameter of 10 mm,
A disk-shaped molded body having a thickness of 0.5 mm was obtained.

Next, this molded body is exposed to the atmosphere (oxidizing atmosphere).
By firing at 1300 ° C. for 2 hours in the inside, the dielectric ceramic base body 12 shown in FIG. 1 made of a sintered body was obtained. Next, a silver paste is applied to one and both main surfaces of the porcelain substrate 12 by a printing method and then baked at 800 ° C. to form a pair of electrodes 14 and 16 to complete the porcelain capacitor 10. .

Next, the maximum relative permittivity ε _max , tan δ, resistivity ρ, and average particle diameter D of the completed ceramic capacitor were measured in the following manner. (A) Maximum relative permittivity Put a porcelain capacitor in a constant temperature bath to -25 ℃ to + 85 ℃
The maximum capacitance when the temperature was changed to was measured under the conditions of 1 kHz and 1 V using an impedance analyzer, and the relative permittivity was calculated based on the maximum capacitance and the dimensions of the porcelain substrate. (B) tan δ (dielectric loss) tan δ at 20 ° C was measured. (C) Resistivity ρ The pair of electrodes 14 and 16 was set to 150 ° C.
In the meantime, 100 V DC was applied for 20 seconds to measure the insulation resistance, and the resistivity ρ was calculated from the value of this insulation resistance and the size of the porcelain substrate 12. (D) Average Grain Size The surface of the porcelain substrate 12 before forming the electrodes 14 and 16 was randomly selected at 5 locations, and these were scanned with a scanning electron microscope for 200 times.
The image was magnified at 0 times or 5000 times, and 200 crystal grains were randomly selected from these photographs and the size was measured by the intercept method, and the average value was determined to be the average particle size. The presence or absence of giant particles in the porcelain substrate 12 was also examined. For the determination of the giant particles, the surface of the porcelain substrate 12 whose average particle diameter was measured was observed with an electron microscope at a magnification of 100 times, and particles having an average particle diameter D of 10 times or more were regarded as giant particles. Table 2 shows the electrical characteristics of each sample, the average particle size, and the presence or absence of giant particles.

[0015]

[Table 2]

In the case of sample No. 1, as is clear from Table 2, the maximum relative permittivity ε _max is 23400 and the dielectric loss tan is
δ is 0.59%, resistivity ρ is 1.08 × 10 ⁶ MΩ · c
m, the average particle size was 2.7 μm, and no giant particles existed.

Also in sample Nos. 2 to 23, porcelain capacitors were made in the same manner as in sample No. 1, and ε was made in the same manner.
_{The max} , tan δ, ρ, and D were measured, and the presence or absence of giant particles was determined.

As is clear from Tables 1 and 2, sample Nos. 1, 3, 4, 7, which satisfy the composition specified in the present invention,
8, 11, 12, 15, 16, 19, 20, 22, 23
The porcelain capacitor of -25 ° C which is the target of the present invention
The maximum relative permittivity ε _max in the range of + 85 ° C is 140
0 or more, tan δ at 20 ° C. is 1.5% or less, resistivity ρ at 150 ° C. is 5 × 10 5 MΩ · cm or more, average particle diameter D
Is 4 μm or less, which means that there is no giant particle. On the other hand, sample Nos. 2, 5, 6, 9, 10, 13, 1 in Table 1 and Table 2
The ceramic capacitors 4, 17, 18, and 21 are not included in the present invention because the characteristics targeted by the present invention cannot be obtained.

Next, the reasons for limiting the composition of the dielectric ceramic will be described. As shown in sample No. 2, when β is 0, large particles are generated and ε _max is less than 14,000. However, as shown in Sample No. 3, the desired characteristics are obtained when β is 0.01. Therefore, the lower limit of β is 0.01. As shown in sample No. 5, when β is 0.13, ε _max is less than 14,000. However, as shown in sample No. 4, when β is 0.12, the desired characteristics are obtained. Therefore, the upper limit of β is 0.12.

As shown in sample No. 6, when γ is 0.002, huge particles are generated and ρ is less than the target value. However, as shown in sample No. 7, when γ is 0.003, desired characteristics are obtained. Therefore, the lower limit of γ is 0.00
It is 3. As shown in sample No. 9, when γ is 0.035, ε _max is less than 14,000. However, sample N
As shown in O.8, desired characteristics are obtained when γ is 0.030. Therefore, the upper limit of γ is 0.030.

As shown in sample No. 10, k was 0.994.
In case of, huge particles are generated. However, sample No. 11
When k is 0.996, the desired characteristics are obtained as shown in FIG. Therefore, the lower limit value of k is 0.996. Sample N
As shown in O. 13, when k is 1.035, a dense sintered body cannot be obtained. However, as shown in sample No. 12, when k is 1.030, the desired characteristics are obtained. Therefore, the upper limit value of k is 1.030.

As shown in sample No. 14, x is 0.08
When 0, ε _max is less than 14000, and tan
δ becomes larger than 1.5%. However, sample No. 15
When x is 0.100, the desired characteristics are obtained as shown in FIG. Therefore, the lower limit of x is 0.100. Sample No.
As shown in 17, when x is 0.230, ε _max is less than 14000. However, as shown in sample No. 16, when x is 0.20, desired characteristics are obtained. Therefore, the upper limit of x is 0.20.

Note that α is 0.996 ≦ k = α + β + γ
The value is in a range satisfying the formula of ≦ 1.030.

As shown in Sample No. 18, NiO or Z
When no nO is added, ρ becomes less than 5 × 10 ⁵ MΩ · cm, and the average particle diameter D becomes larger than 4 μm.
However, as shown in sample NO19, the desired characteristics are obtained when the NiO content is 0.002 parts by weight. Although not shown in Table 1 and Table 2, ZnO was replaced by ZnO in place of NiO.
The desired characteristics were also obtained when 002 parts by weight was added and when 0.002 parts by weight of the mixture of NiO and ZnO was added. Therefore, the lower limit of the amount of NiO and / or ZnO added is 0.002 parts by weight. When NiO is 0.550 parts by weight in sample No. 21, ε _max is less than 14,000 and ρ is less than 5 × 10 ⁵ MΩ · cm. However, as shown in Sample No. 20, when NiO is 0.500 parts by weight, desired characteristics are obtained. Although not shown in Tables 1 and 2, ZnO is added in an amount of 0.50 instead of NiO.
The desired characteristics can be obtained even when 0 part by weight is added or when 0.50 parts by weight of NiO and ZnO are mixed and added. Therefore, the upper limit of the amount of NiO and / or ZnO added is 0.500 parts by weight.

[0025]

[Second Embodiment] FIG. 2 shows a laminated ceramic capacitor 18 according to a second embodiment. This porcelain capacitor 18 includes a dielectric porcelain substrate 20, a plurality of first inner electrodes 22, a plurality of second inner electrodes 24, first and second outer electrodes 26, 2.
8 and. The dielectric ceramic body 20, similarly to the dielectric ceramic substrate 12 of FIG. 1, the basic components of 100 parts by weight consisting of _{(Ba α Ca β Er γ O} k) (Ti 1-x Zr x O 2), 0 .002-0.
It is formed of a composition consisting of 500 parts by weight of zinc oxide and / or nickel oxide. The first and second internal electrodes 22 and 24 are embedded in the dielectric ceramic base 20, respectively,
One ends of these are exposed at the pair of side surfaces of the dielectric ceramic base 20, and the first and second external electrodes 26, 2 provided there are provided.
8 is connected. First and second internal electrodes 22, 2
Since 4 are opposed to each other via the dielectric ceramic layer formed of a part of the dielectric ceramic base 20, it is possible to obtain these capacitances.

When manufacturing a laminated ceramic capacitor,
As is well known, a plurality of green sheets (unfired ceramic sheets) made of a dielectric ceramic material are prepared. Next, the first and second internal electrodes 22, 2 are formed on the plurality of green sheets.
In order to obtain 4, a conductive paste containing a mixture of Ag (silver) and Pd (palladium) as a conductive material is applied in a desired pattern and laminated, and the conductive paste is further laminated on the upper and lower sides, and these are pressure-bonded. Cut to desired shape and bake. As a result, the porcelain substrate 20 with the first and second internal electrodes 22 and 24 shown in FIG. 2 is obtained. Then, a conductive paste (Ag paste) is applied to the side surface of the porcelain substrate 20 and baked to form the first and second external electrodes 26 and 28.

As with the porcelain capacitor 10 of FIG. 1, the multilayer capacitor 18 of FIG.
3, 4, 7, 8, 11, 12, 15, 16, 19, 2
Samples with the same composition as 0, 22, and 23 are made,
When these ε _max , tan δ, ρ, D, and giant particles were measured, the target characteristics of the present invention were satisfied.

[0028]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) The firing temperature can be changed, for example, in the range of 1000 to 1400 ° C. Also, the temperature of calcination is set to, for example, 10
It can be changed within the range of 00 to 1300 ° C. (2) Er ₂ O ₃ as a starting material for the dielectric ceramic material
Alternatively, an erbium compound such as Er (OH) ₃ can be used. (3) Oxides, hydroxides and the like can be used as starting materials for the dielectric ceramic material. (4) Ag is used as a conductive material for obtaining the internal electrodes.
Pd instead of a mixture with (silver) Pd (palladium)
(Palladium) 100% can be used.

[Brief description of drawings]

FIG. 1 is a front view showing a porcelain capacitor of a first embodiment.

FIG. 2 is a sectional view showing a laminated ceramic capacitor of a second embodiment.

[Explanation of symbols]

 12 Dielectric Porcelain Substrate 14, 16 Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Shibuya 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Induction Co., Ltd.

Claims (2)

[Claims] 1. (Ba _α Ca _β Er _γ O _k ) (Ti _1-x
Zr _x O ₂ ) where α, β, γ, k, and x are 0.01 ≦ β ≦ 0.12 0.003 ≦ γ ≦ 0.03 0.996 ≦ α + β + γ = k ≦ 1.030 0. 100 parts by weight of a basic component consisting of 10 ≦ x ≦ 0.20, and 0.002 to 0.500 parts by weight of an additive component consisting of one or both of zinc oxide and nickel oxide. Dielectric porcelain containing. 2. A porcelain capacitor comprising a dielectric porcelain base and at least two electrodes in contact with the dielectric porcelain base, wherein the dielectric porcelain base is (Ba _α Ca _β Er _γ O _k ). (Ti _1-x Zr _x O ₂ ) where α, β, γ, k and x are 0.01 ≦ β ≦ 0.12 0.003 ≦ γ ≦ 0.03 0.996 ≦ α + β + γ = k ≦ 1.030 100 parts by weight of the basic component consisting of 0.10 ≦ x ≦ 0.20 and 0.002 to 0.500 parts by weight of zinc oxide and / or nickel oxide. A dielectric ceramic capacitor characterized by comprising an additive component consisting of.