JPH06267331A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To fabricate a composition from which a dielectric porcelain having a high dielectric constant and small dielectric loss is made by containing a specific amount of manganese compound in a composition comprising BaO, MgO, CaO, SrO, TiO2, and NdO3/2 blended together in a specific ratio. CONSTITUTION:A manganese compound as an auxiliary component is contained by 0.01 to 1.00 parts by weight as MnO2 in 100 parts by weight of a composition represented by a general formula: x[(BaO)(1-k-m-n)(MgO)k(CaO)-m(SrO)n] . yTiO2 .zNdO3/2 wherein 0.01<=(k)<=0.100, 0.005<=(m)<=0.200, 0.005<=(n)<=0.200, (x), (y), (z) represent mole ratios, (x)+(y)+(z)= 1, and the mole ratios represented by (x), (y), (z) are in the range surrounded by (a), (b), (c), (d). A composition from which a dielectric porcelain having great dielectric breakdown voltage, great insulation resistance and small crystal grain size is made is thus fabricated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition having a high dielectric constant, a small dielectric loss, a large dielectric breakdown voltage and a large insulation resistance, and a small crystal grain size.

[0002]

2. Description of the Related Art Conventionally, as a dielectric ceramic composition having a high dielectric constant, BaTiO ₃ , BaO, CaO, Ti has been used.
It is known that O ₂ and ZrO ₂ are added in appropriate amounts.

[0003]

However, since these dielectric ceramic compositions have a large crystal grain size of 10 to 20 μm and a high porosity, they are applied to products having a thin dielectric thickness such as a laminated ceramic capacitor. Have problems such as increased dielectric loss, low dielectric breakdown voltage, and reduced dielectric breakdown voltage and insulation resistance during plating processing for forming external electrodes.

[0004]

In order to solve these problems, the present invention uses x [(BaO) _(1-km
-n) (MgO) _k (CaO) _m (SrO) _n ] .yTiO ₂
Represented by zNdO _3/2 , having a composition in which m = 0, n = 0 and the value of k is in the range of 0.001 ≦ k ≦ 0.100,
X, y and z represent a molar ratio, and x + y + z = 1, and the composition of x, y and z is in the range of molar ratios surrounded by a, b, c and d shown in (Table 1). Then, the manganese compound is converted into the form of MnO ₂ as an auxiliary component and converted to 0.0.
The present invention provides a dielectric ceramic composition containing 1 to 1.00 parts by weight.

According to the present invention, in the above general formula, n =
0 and the values of k and m are 0.001 ≦ k ≦ 0.
100, a dielectric ceramic composition having a composition in the range of 0.005 ≦ m ≦ 0.200, or in the above general formula, when m = 0, the values of k and n are 0.001 respectively.
Dielectric ceramic composition having a composition in the range of ≦ k ≦ 0.100, 0.005 ≦ n ≦ 0.200, or in the above general formula, when k = 0, the values of m and n are respectively:
0.005 ≦ m ≦ 0.200, 0.005 ≦ n ≦ 0.2
In the above general formula, the values of k, m and n are 0.001 ≦ k ≦ 0.100 and 0.005 ≦ m ≦, respectively.
The present invention provides a dielectric ceramic composition having a composition of 0.200 and 0.005 ≦ n ≦ 0.200. Furthermore, niobium oxide is added as a subcomponent to Nb ₂
The present invention provides a dielectric ceramic composition obtained by adding 0.3 to 3.0 parts by weight in terms of O ₅ .

[0006]

With this structure, by replacing BaO with MgO, the dielectric loss is reduced and the product of the capacitance and the insulation resistance (CR product) is increased.

By replacing BaO with CaO, the dielectric loss is reduced, and BaO is replaced with SrO.
By replacing with, the dielectric loss is reduced without lowering the dielectric constant, and the product of the capacitance and the insulation resistance (CR product) is increased. Therefore, the combination of these results in a high dielectric constant,
The dielectric loss is small and the CR product is large.

The inclusion of a manganese compound as an auxiliary component has the effect of increasing the CR product, and the content ratio of MnO ₂ is 100 parts by weight of the main component.
If it is less than 0.01 parts by weight or more than 1.00 parts by weight, the CR product will decrease.

Further, by adding niobium oxide as a sub ingredient, the CR product and the dielectric breakdown strength are increased.

Furthermore, with these structures, a dielectric ceramic having a small crystal grain size can be obtained, so that the dielectric thickness can be reduced, and the product can be downsized and the capacity can be increased.

[0011]

【Example】

Example 1 As a starting material, chemically pure BaC is used.
O ₃ , MgO, TiO ₂ , Nd ₂ O ₃ and MnO ₂ powders were weighed so as to have the composition ratios shown in (Table 2) below, put into a rubber-lined ball mill equipped with agate balls together with pure water, and wet. After mixing, it was dehydrated and dried. This dry powder was placed in a crucible of high alumina quality, and the powder was placed in air at 1100 ° C. for 2 hours.
I calcined for an hour. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, wet pulverized, and then dehydrated and dried. An organic binder was added to this pulverized powder to make it homogenous, and then the powder was sized through a 32 mesh sieve and molded into a diameter of 15 mm and a thickness of 0.4 mm at a molding pressure of 1 t / cm ² using a mold and a hydraulic press. Next, this molded disc is put into an alumina-made sheath coated with zirconia powder, and fired in air at a firing temperature shown in (Table 2) for 2 hours to obtain a dielectric ceramic circle having a composition ratio shown in (Table 2). I got a plate.

The thickness and diameter of the dielectric ceramic disk thus obtained were measured, and the samples for measuring the dielectric constant, dielectric loss and capacitance temperature characteristic were silver on both sides of the dielectric ceramic disk. The electrodes were baked, and for the samples for measuring the dielectric breakdown voltage and the insulation resistance, the silver electrodes were baked to 1 mm inside from the outer circumference of the dielectric ceramic disk. The dielectric constant, the dielectric loss, and the capacitance-temperature characteristic were measured by using a Yokogawa Hewlett-Packard Co., Ltd. digital LCR meter model 4274A at a measurement temperature of 20 ° C., a measurement voltage of 1 Vrms, and a measurement frequency of 1 KHz. I asked.

The rate of change in capacitance temperature represents the rate of change with capacitance at any measurement temperature within the temperature range of -25 ° C to + 85 ° C, with 20 ° C as the reference temperature. The rate of change was calculated from the following formula.

DC = (C _T -C _O ) / C _O × 100 dC: Capacitance temperature change rate (%) C _T : Capacitance at T ° C. (pF) C _O : Electrostatic at 20 ° C. Capacitance (pF) Then, the dielectric constant was obtained from the following equation.

K = 143.8 × C _O × t / D ² K: Dielectric constant C _O : Capacitance (pF) at 20 ° C. D: Diameter of dielectric ceramic disk (mm) t: Dielectric ceramic Disc thickness (mm) The breakdown voltage was measured by using a high voltage DC power supply PHS35K-3 type manufactured by Kikusui Electronics Co., Ltd., putting the sample in silicone oil, and measuring it at a boosting speed of 50 V / s. It was calculated from the formula as the dielectric breakdown strength per 1 mm of the dielectric.

B ₁ = B _O / t B ₁ : Dielectric breakdown strength (KV / mm) B _O : Dielectric breakdown voltage (KV) Further, the insulation resistance is measured by using a high resistance meter manufactured by Takeda Riken Co., Ltd. Measurement voltage 50V. It was obtained from the measurement at DC for 1 minute, and the CR product was obtained from the following equation.

CR = C _O × R _O / 10 ¹² CR: CR product (MΩ · μF) C _O : capacitance at 20 ° C. (F) R _O : insulation resistance (Ω) Further, the crystal grain size is , And was obtained by observation with an optical microscope at a magnification of 400. The measurement results are shown in (Table 3) for each of the sample numbers 1 to 16.

[0018]

[Table 2]

[0019]

[Table 3]

FIG. 1 is a ternary diagram showing the composition range of the main component according to the present invention, and the reason why the composition range of the main component is limited will be described with reference to FIG. That is, the dielectric constant is small in the A region, which is not practical. Further, in the region B, the Curie point becomes too large on the minus side, and the rate of capacitance temperature change of the temperature characteristic largely deviates to the plus side, which is not practical. Further, sintering is extremely difficult in the C region.
Furthermore, the dielectric constant is small in the D region, which is not practical.

Further, by substituting MgO for BaO, the dielectric loss can be reduced without largely changing the dielectric constant and the dielectric breakdown strength, and the product of the electrostatic capacity and the insulation resistance (CR product).
However, the replacement rate k is 0.
If it is less than 001, there is no effect, while if it exceeds 0.100, the dielectric constant decreases and it becomes impractical.

Further, the crystal grain size can be reduced to 5 to 10 μm. (Example 2) High-purity CaCO ₃ powder was weighed so as to have the composition ratio shown in (Table 4) in Example 1, and the subsequent steps were processed in the same manner as in Example 1 to obtain a sample of (Table 4). Numbers 17-32
The results obtained by obtaining the dielectric ceramic disk having the composition ratio shown in Table 1 and treating it in the same manner as in Example 1 and measuring the electrical characteristics and the crystal grain size are shown in Table 5 for each of sample numbers 17 to 32.

[0023]

[Table 4]

[0024]

[Table 5]

The reason why the composition range of the main component is limited is the same as that of the first embodiment, and the description thereof will be omitted.

Also, by substituting BaO with MgO and CaO, it has the effect of reducing the dielectric loss without significantly changing the dielectric constant, dielectric breakdown strength and CR product, but the substitution rate k of MgO is If it is less than 0.001, there is no effect, while if it exceeds 0.100, the dielectric constant decreases and it becomes impractical. Further, the substitution rate m of CaO is 0.005.
If it is less than 0.20, there is no effect. On the other hand, if it exceeds 0.200, the sinterability is deteriorated and the dielectric constant is lowered, which is not practical.

(Example 3) High-purity SrCO was used in Example 1.
_{The three} powders were weighed so as to have the composition ratio shown in (Table 6), and the subsequent steps were processed in the same manner as in Example 1 to obtain dielectric ceramic circles having the composition ratios shown in sample numbers 33 to 48 of (Table 6). A plate was obtained, treated in the same manner as in Example 1, and the electrical characteristics and the crystal grain size were measured. The results are shown in Table 7 for each of sample numbers 33 to 48.

[0028]

[Table 6]

[0029]

[Table 7]

The reason why the composition range of the main component is limited is the same as that of the first embodiment, and the description thereof will be omitted.

Further, by substituting BaO with MgO and SrO, it has the effect of reducing the dielectric loss and increasing the CR product without significantly changing the dielectric constant and dielectric breakdown strength, but the substitution rate k of MgO is k. Is less than 0.001, there is no effect, while if it exceeds 0.100, the dielectric constant decreases and it becomes impractical. Further, the substitution ratio n of SrO is 0.00
If it is less than 5, there is no effect. On the other hand, if it exceeds 0.200, the dielectric constant decreases and it becomes impractical.

Further, the crystal grain size can be reduced to 5 to 10 μm. (Example 4) Instead of the high-purity MgO of Example 1, high-purity CaCO ₃ and SrCO ₃ powders were weighed so that the composition ratio shown in (Table 8) was obtained, and the subsequent steps were performed as in Example 1. Samples Nos. 49 to 64 having the composition ratios shown in Table 8 were treated in the same manner to obtain dielectric ceramic disks, and treated in the same manner as in Example 1 to measure the electrical characteristics and the crystal grain size. 49 ~
It is shown in 64 (Table 9).

[0033]

[Table 8]

[0034]

[Table 9]

The reason why the composition range of the main component is limited is the same as that of the first embodiment, and the description thereof will be omitted.

Further, by substituting BaO with SrO and CaO, it has the effect of reducing the dielectric loss and increasing the CR product without significantly changing the dielectric constant and dielectric breakdown strength. Is less than 0.005, there is no effect, while if it exceeds 0.200, the sinterability deteriorates and the dielectric constant decreases, making it impractical. Further, if the substitution ratio n of SrO is less than 0.005, there is no effect, while 0.2
If it exceeds 00, the dielectric constant is lowered and it becomes impractical.

Further, the crystal grain size can be reduced to 5 to 10 μm. (Example 5) High-purity CaCO Example 1 ₃ and Sr
The CO ₃ powder was weighed so that the composition ratio shown in (Table 10) was obtained, and the subsequent steps were treated in the same manner as in Example 1 (Table 10).
Sample Nos. 65 to 80 of the dielectric ceramic plate were obtained, treated in the same manner as in Example 1 and measured for electrical characteristics and crystal grain size. Show.

[0038]

[Table 10]

[0039]

[Table 11]

The reason why the composition range of the main component is limited is the same as in Example 1, and therefore the description thereof is omitted.

Further, BaO is replaced with MgO, CaO and Sr.
Substitution with O has the effect of reducing the dielectric loss without significantly changing the dielectric constant, dielectric breakdown strength and CR product, but if the substitution rate k of MgO is less than 0.001, it has no effect. If it exceeds 0.100, the dielectric constant is lowered and it becomes impractical. Further, the substitution rate m of CaO is 0.
If it is less than 005, there is no effect. On the other hand, if it exceeds 0.200, the sinterability deteriorates, and the dielectric constant decreases, making it impractical.
Further, if the substitution ratio n of SrO is less than 0.005, there is no effect, while if it exceeds 0.200, the dielectric constant decreases and it becomes impractical.

Further, the crystal grain size can be reduced to 5 to 10 μm. (Example 6) High-purity N was added to the representative samples of Examples 1-5.
The b ₂ O ₅ powder was weighed so as to have the composition ratio shown in (Table 12), and the subsequent steps were treated in the same manner as in Example 1 (Table 12).
Sample Nos. 81 to 93 of the dielectric ceramic plates having composition ratios shown in Table 1 were obtained by treating samples in the same manner as in Example 1 for electrical characteristics and crystal grain size. Show.

[0043]

[Table 12]

[0044]

[Table 13]

The reason why the composition range of the main component is limited is the same as that of the first embodiment, and the description thereof will be omitted.

By containing the sub-component Nb ₂ O ₅ with respect to the main component, it has the effect of improving the product of electrostatic capacity and insulation resistance (CR product) and the dielectric breakdown voltage. If it is less than 0.3 parts by weight with respect to 100 parts by weight of the main component, there is no effect of inclusion. On the other hand, if it exceeds 3.0 parts by weight, the Curie point shifts to the negative side and the dielectric constant is lowered, which is not practical.

Further, the crystal grain size can be reduced to 3 to 8 μm. In each of the above Examples, the inclusion of MnO ₂ as a sub-component has the effect of improving the CR product, but as shown in (Table 12) and (Table 13) of Example 6, If the content is less than 0.01 parts by weight with respect to 100 parts by weight of the main component, there is no effect of increasing the CR product, and if it exceeds 1.00 parts by weight, C
The R product decreases and becomes impractical. This is Example 1-5
It was exactly the same in.

In the method for producing the dielectric ceramic composition in the examples, BaCO ₃ , MgO, SrCO ₃ and CaC are used.
O ₃ , TiO ₂ , Nd ₂ O ₃ , Nb ₂ O ₅ and MnO ₂ were used, but the method is not limited to this, and a compound such as BaTiO ₃ or a carbonate may be used so as to obtain a desired composition ratio. , Ba by heating in air such as hydroxide
O, MgO, SrO, CaO, TiO ₂ , Nd ₂ O ₃ , N
Even if a compound that becomes b ₂ O ₅ and MnO ₂ is used, it is possible to obtain characteristics similar to those of the examples.

Further, the industrially used BaT which is generally used
The Ba / Ti ratio of iO ₃ is 0.98 or more.
When O ₃ is used as a starting material, the same level of characteristics as in the example can be obtained even if a shortage of BaO or TiO ₂ is added.

Further, even if the main component is pre-calcined in advance and the sub-components are added, the same characteristics as those of the embodiment can be obtained.

Further, titanium dioxide, which is an industrial raw material generally used for dielectric porcelain, such as titanium dioxide KA-10 manufactured by Titanium Industry Co., Ltd. and titanium dioxide FA-55W manufactured by Furukawa Mining Co., Ltd. has a maximum of 0. .45 wt% Nb
₂ O ₅ is contained, but even if a dielectric ceramic of the main component is made using these titanium dioxides, the maximum content of Nb ₂ O ₅ is 0.17 wt% with respect to 100 wt% of the main component. %, Which is out of the range of the present invention, but by considering the amount of Nb ₂ O _{5 in} titanium oxide, which is a raw material for industrial use, and adding a shortage of Nb ₂ O ₅ , the same characteristics as those of the example were obtained. Can be obtained.

In addition to the above basic composition, Zn
It is also possible to add salts, oxides, etc., which are generally considered to be fluxes, such as O, SiO ₂ , Fe ₂ O _3, etc. within a range that does not impair the characteristics.

[0053]

As described above, according to the present invention, by replacing BaO with SrO, which has a high dielectric constant, the dielectric loss can be reduced without largely changing the dielectric constant and dielectric breakdown strength, and The product of the capacitance and the insulation resistance (CR product) can be increased. In addition, the CR product can be increased by adding manganese as an accessory component. Furthermore, the CR product and the dielectric breakdown strength can be increased by adding niobium as an accessory component. Further, with these configurations, a dielectric ceramic having a small crystal grain size can be obtained. Therefore, the thickness of the dielectric can be reduced, and the product can be downsized and the capacity can be increased.

[Brief description of drawings]

FIG. 1 is a ternary diagram showing a composition range of a dielectric ceramic composition according to claim 1 of the present invention.

Claims (6)

[Claims] 1. The general formula x [(BaO)]_(1-kmn)
(MgO)_k(CaO) _m(SrO)_n] ・ YTiO₂・ Z
NdO_3/2And m = 0, n = 0, and the value of k is 0.0
Has a composition in the range of 01 ≦ k ≦ 0.100, and
x, y and z represent a molar ratio, x + y + z = 1, and x,
The values of y and z are as shown in Table 1.In the range of molar ratios surrounded by a, b, c and d
And a manganese compound as a sub-component.
O₂0.01 to 1.00 parts by weight
Dielectric porcelain composition. 2. When n = 0 and the values of k and m are respectively:
0.001 ≦ k ≦ 0.100, 0.005 ≦ m ≦ 0.2
The dielectric ceramic composition according to claim 1, which has a composition in the range of 00. 3. When m = 0, the values of k and n are respectively:
0.001 ≦ k ≦ 0.100, 0.005 ≦ n ≦ 0.2
The dielectric ceramic composition according to claim 1, which has a composition in the range of 00. 4. When k = 0, the values of m and n are respectively:
0.005 ≦ m ≦ 0.200, 0.005 ≦ n ≦ 0.2
The dielectric ceramic composition according to claim 1, which has a composition in the range of 00. 5. The values of k, m and n are each 0.0.
01 ≦ k ≦ 0.100, 0.005 ≦ m ≦ 0.200,
The dielectric ceramic composition according to claim 1, which has a composition in the range of 0.005 ≦ n ≦ 0.200. 6. The dielectric material according to claim 1, wherein 0.3 to 3.0 parts by weight of niobium oxide is added as a subcomponent in the form of Nb ₂ O _5. Porcelain composition.