JPH0536308A - High permittivity dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a high permittivity dielectric ceramic composition excellent in such properties that variation of permittivity is small in wide temperature range and dielectric loss is little. CONSTITUTION:CaZrOe3 of 0.2-7.0weight% as an additive is included in a high permittivity dielectric ceramic composition of which main component consists of BaTiO3: 94.0-99.0mole%, Nb2O5: 0.5-3.0mole% and NiO: 0.5-3.0mole%. Further, 0.7weight% of one out of La2O3, Nd2O3, and Sm2O3 is included in this composition. MnO of 0.3weight% or less is also included in the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-dielectric-constant dielectric ceramic composition, which has a small change in dielectric constant over a wide temperature range and a small dielectric loss. The present invention relates to a high dielectric constant dielectric porcelain composition that can be used in a place exposed to heat.

[0002]

2. Description of the Related Art Barium titanate (Ba) has hitherto been used as a dielectric ceramic composition having a high dielectric constant and a small temperature change.
TiO ₃ ), a bismuth compound such as Bi ₂ O ₃ , 2S
nO ₂ , Bi ₂ O ₃ , 2ZrO ₂ and Ta ₂ O ₃ and Nb
A material was used in which the rate of change in temperature characteristics was reduced by adding ₂ O ₅ or the like.

[0003]

However, in the composition containing the above-mentioned components, when the dielectric constant is increased, the rate of change in electrostatic capacity becomes large, and there is a limit to increase the dielectric constant. Therefore, when the composition is used in a capacitor, it is difficult to obtain a small size and a large capacity,
The X7R characteristic (capacitance change rate of ± 15% at −55 ° C. to + 125 ° C.) was the limit.

The composition containing a bismuth compound like the above-mentioned composition has a problem that the bismuth component evaporates during firing and the porcelain composition body is bent. Furthermore,
When a barium titanate laminated porcelain capacitor containing bismuth is manufactured, the internal electrode palladium or the silver-palladium alloy reacts with bismuth, which is a component of the dielectric, and loses its function as an electrode. As a result, expensive platinum must be used, which has been a factor in increasing the cost of the laminated porcelain capacitor.

An object of the present invention is to solve such conventional problems and to provide an excellent high-dielectric-constant porcelain composition having a small dielectric constant change over a wide temperature range and a small dielectric loss. To do.

[0006]

In order to achieve the object In order to achieve the object, the present inventors as a result of intensive studies, as a main component, BaTiO _3: from 94.0 to 99.0 mol% Nb ₂ O _5: 0.5~ 3.0 mol% NiO: It was found that the Curie point is shifted to the temperature + side by adding CaZrO ₃ in an amount of 0.2 to 7.0% by weight with respect to 0.5 to 3.0 mol%.

Also, if necessary, La ₂ O ₃ , Nd ₂
It has been found that the characteristics are excellent when one of O ₃ and Sm ₂ O ₃ is contained in an amount of 0.7% by weight or less. By further adding 0 to 0.3% by weight of MnO to these, the characteristics are further improved.

[0008]

By using the dielectric ceramic composition of the present invention, the dielectric constant at room temperature has a high dielectric constant value of 2000 to 4700 and the dielectric loss (tan δ) is 1.2% or less. It is a small value, and the change in dielectric constant with temperature is EIAJ
X7R characteristics (-55
Satisfies the change of dielectric constant within ± 15% in the temperature range of ℃ to + 125 ℃, and further X8R characteristics (-55 ℃ to + 150 ℃)
Change of the dielectric constant within ± 15% in the temperature range of
It was possible to obtain a high dielectric constant dielectric ceramic composition having excellent characteristics that the transverse rupture strength was also increased.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views showing an embodiment of the present invention. FIG. 1 is a ternary composition diagram of a high dielectric constant dielectric ceramic composition, and FIG. 2 is a high dielectric constant dielectric ceramic composition. Manufacturing process drawing, FIG. 3 is a temperature characteristic curve of capacitance, and FIG. 4 is 98.BaTiO 3.
_{3 -1 · Nb 2 O 5 -1} · NiO + CaZrO 3 added-amount Curie point position and shows a dielectric constant at 25 ° C., _{5, 98 · BaTiO 3 -1 · Nb} 2 O 5
FIG. 3 is a diagram showing bending strength when different amounts of −1 · NiO + CaZrO _{3 are} added.

First, the manufacturing process of the high dielectric constant dielectric ceramic composition of this embodiment will be described with reference to FIG. The step numbers in FIG. 2 are shown in parentheses.

As a starting material, BaCO ₃ and TiO ₂ are mixed at a molar ratio of 1: 1 (S1), and the prepared starting material is dehydrated and dried (S2). Next, these raw materials are preliminarily molded, stabilized at 1000 to 1200 ° C. for 2 hours to cause a chemical reaction, and prebaked to form BaTiO ₃ (S3). This BaTiO ₃ is crushed by, for example, an atomizer (S4).

[0012] Thus BaTiO ₃ obtained or BaTiO so that BaTiO ₃ powder obtained by adjusting the solution method the composition after firing becomes a predetermined composition _3,
Nb ₂ O ₅ , NiO, La ₂ O ₃ , Nd ₂ O ₃ , Sm ₂
O ₃ , CaZrO ₃ , MnCO ₃ etc. are weighed (S5),
Wet mixing (S6), dehydration and drying (S7).

An appropriate amount of organic binder is added to this, and about 3
Molded at a molding pressure of t / cm ² , diameter 16.5mm, thickness 0.6mm
A disk-shaped molded article of is prepared. Next, 122
Perform stable main firing at 0 to 1340 ° C. for 2 hours (S
8).

Silver electrodes are baked on both ends of the obtained ceramic composition body to obtain a capacitor (S9). Finally, the respective electrical characteristics of the capacitors, the frequency 1 kH _Z, measured under the conditions of room temperature 20 ℃ (S10). The measurement results are shown in Tables 1 and 2.

[0015]

[Table 1]

[0016]

[Table 2]

In the above measurement, as shown in Tables 1 and 2, the data of the samples No. 1 to 10 were measured. According to the result, in the samples of Table 1 and Table 2, sample No. 1,
3, 3-4, 3-7, 3-9, 3-11, 3-15, 3
-17, 6, 8, and 10 are not included in the scope of the present invention (samples indicated by X in the table).

The dielectric ceramic composition of the present invention comprises BaTi
O _3: 94.00 to 99.00 mol%, Nb ₂ O _5: 0.50~3.0
Mol%, NiO: 0.50 to 3.0 mol% as a main component and 0.2 to 7.0 wt% of CaZrO ₃ as an additive, and if necessary, an additive, La ₂ O ₃ , Nd ₂
One of O ₃ and Sm ₂ O ₃ is contained in an amount of 0.70% by weight or less. The characteristics are further improved by adding 0 to 0.3% by weight of MnO.

FIG. 1 shows a ternary component diagram composed of the compositions of the main components. In FIG. 1, the number of each point corresponds to the sample No. in Table 1. Next, the reasons for limiting the composition range of the present invention as described above will be described with reference to Tables 1 and 2. The circles in front of the sample Nos. In Tables 1 and 2 are
Samples that fall within the scope of the present invention, and marks x are samples that fall outside the scope of the present invention.

When BaTiO ₃ is less than 94.00 mol%, the relative dielectric constant (ε _S ) becomes low (see Sample No. 6),
If it exceeds 99.0 mol%, the dielectric body is reduced and blackened (see Sample No. 1).

If Nb ₂ O ₅ is less than 0.5 mol%, it is similarly reduced and blackened and measurement becomes impossible (see Sample No. 1), and if it exceeds 3.0 mol%, ε _S becomes low (Sample No. 1). 6 and 10), and ΔC / C25 ° C. increases (see Sample Nos. 6 and 10).

Further, if NiO is less than 0.5 mol%,
The dielectric body is reduced and blackened and measurement becomes impossible (see Sample No. 1), and when it exceeds 3.0 mol%, ε _S becomes low (see Sample No. 6) and ΔC / C25 ° C becomes large (Sample No. 1). .6, 8).

There is no problem in use even if one of La ₂ O ₃ , Nd ₂ O ₃ and Sm ₂ O ₃ is not added to the above main component (Sample Nos. 2, 3-1, 3). -2, 3-3, 3-
5), the sinterability is improved by adding 0.7% by weight or less (see Sample No. 3-6, 3-8, 3-10), and if it exceeds 0.7% by weight, ΔC / C25 ° C increases and X8R characteristics It comes off (see Sample No. 3-7, 3-9, 3-11).

If CaZrO ₃ is less than 0.2% by weight, ΔC /
C25 ℃ becomes large, X8R characteristic is lost (Sample No.
3), ΔC / C25 ° C increases even if it exceeds 7.0% by weight, and the X8R characteristic is no longer satisfied (Sample No. 3-4).
reference).

Although the addition of MnO does not cause any problem in use without addition (Sample Nos. 2, 3-1, 3-2, 3-3, 3-5,
3-6, 3-8, 3-10, 3-16, 4, 5, 7, 9
), Tan δ
Is improved and sinterability is also improved (Sample No. 3-12, 3
-13, 3-14).

If the amount of MnO added exceeds 0.3% by weight, ΔC / C25 ° C. increases, tan δ deteriorates, and a dense porcelain cannot be obtained (see Sample No. 3-15).
In addition, SiO ₂ and Al as a trace amount of impurities mixed in the raw materials or alkali metal oxides contained in the manufacturing process.
₂ O ₃ may improve the sinterability but does not deteriorate the properties.

In addition, the method of adding NiO and Nb ₂ O ₅ is as follows. Even if NiO and Nb ₂ O ₅ are added individually,
The effect was the same even when added as a compound with NiO and Nb ₂ O ₅ .

FIG. 3 shows a temperature characteristic curve of capacitance.
The numbers in the figure correspond to the sample No. in Table 1. As is clear from FIG. 3, the ceramic composition having the composition within the range of the present invention has a small temperature change rate (ΔC / C25 ° C.) over a wide temperature range and is stable.

Further, in FIG. 4, 98.BaTiO ₃ -1
- and _{Nb 2 O 5 -1 · NiO +} CaZrO 3 added-amount Curie point position, there is shown a dielectric constant at 25 ° C.. From this figure, it is clear that the composition within the range of the present invention has a high Curie point and a high relative dielectric constant.

Further, in FIG. 5, 98.BaTiO ₃ -1
_{· Nb 2 O 5 -NiO + CaZrO} 3 is shown the addition-amount of flexural strength. From this figure, in the scope of the present invention,
It is clear that the composition has high bending strength and excellent characteristics.

[0031]

As described above, the present invention has the following effects. (1) The dielectric ceramic composition of the present invention has a relative dielectric constant of about 200.
It has a high value of 0 to 4700 and the dielectric loss is 1.2%.
It is a small value below, and the temperature change rate of capacitance is
It satisfies the X7R characteristic specified by EIAJ and further satisfies the X8R characteristic.

(2) It is possible to obtain a high dielectric constant dielectric ceramic composition having a high bending strength. (3) The dielectric ceramic composition does not include bismuth, which easily reacts with palladium or a silver-palladium alloy, so that when a multilayer capacitor is manufactured using this composition as a dielectric layer,
It is possible to use palladium alone or a silver-palladium alloy as the internal electrode. Therefore, it is not necessary to use expensive platinum or platinum-palladium alloy, and a significant cost reduction of the product can be realized.

[Brief description of drawings]

FIG. 1 is a ternary composition diagram of a high dielectric constant dielectric ceramic composition according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a high dielectric constant dielectric ceramic composition in the same example.

FIG. 3 is a temperature characteristic curve of capacitance in the example.

FIG. 4 is 98 · BaTiO ₃ −1 · N in the example.
and b ₂ O ₅ -NiO + CaZrO ₃ added-amount Curie point position is a diagram showing the dielectric constant at 25 ° C..

FIG. 5: 98 · BaTiO ₃ −1 · N in the same Example
b is a diagram showing the ₂ O ₅ -1 · NiO + flexural strength of CaZrO ₃ amount per time.

Claims (3)

[Claims] As claimed in claim 1 main component, BaTiO _3: from 94.0 to 99.0 mol% Nb ₂ O _5: 0.5 to 3.0 mol% NiO: against 0.5 to 3.0 mol%, as an additive, CaZrO ₃ and 0.2 to 7.0 wt% A high-dielectric-constant dielectric ceramic composition, characterized by containing. 2. The composition is provided with La ₂ O ₃ , Nd.
_2. The high dielectric constant dielectric ceramic composition according to claim 1, which contains 0.7% by weight or less of any one of ₂ O ₃ and Sm ₂ O ₃ . 3. The high dielectric constant dielectric ceramic composition according to claim 1, wherein the composition contains 0.3% by weight or less of MnO.