JPH0782775B2 - Non-reducing dielectric ceramic composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-reducing dielectric porcelain composition for a porcelain capacitor, particularly a laminated porcelain capacitor having internal electrodes made of nickel.

[Conventional technology]

Conventionally, in general, a laminated porcelain capacitor is formed by laminating a plurality of sheet-like dielectrics containing BaTiO ₃ as a main component with internal electrodes coated on the surface, and by alternately arranging the internal electrodes of each sheet in parallel. Is formed by sintering and integrating the same. Such multilayer ceramic capacitors have been rapidly used in a wide range of electronic circuits due to rapid miniaturization of electronic components accompanying the recent progress of electronics.

However, this conventional BaTiO ₃ -based dielectric material must be fired at a high temperature of 1250 ° C to 1350 ° C, and when this material is used as the dielectric of a laminated ceramic capacitor, the internal electrodes are Palladium (melting point 1555 ° C), which is an expensive noble metal that does not melt at the firing temperature of the body and does not oxidize, or its alloy is used. Especially, in the case of large capacitance, the number of internal electrodes becomes large. It had the drawback of high cost. Therefore, the conventional multilayer ceramic capacitor has high capacity efficiency, excellent dielectric characteristics, and high reliability, but its price is a major obstacle to its progress.

Therefore, it has been attempted to use an inexpensive base metal, such as nickel, as the internal electrodes in order to solve the disadvantage that the conventional multilayer ceramic capacitor is expensive. However, when a base metal such as nickel is used as the internal electrode, when the dielectric composed of barium titanate (BaTiO ₃ ) and the base metal internal electrode are simultaneously sintered, the base metal is sintered as a metal film without being oxidized. The condition is that the equilibrium oxygen partial pressure of Ni / NiO is about 3 × 10 ^-7 atm at 1300 ° C.
The oxygen partial pressure should be lower than that, and in this case, the dielectric made of barium titanate or a solid solution thereof is generally reduced under the above-mentioned oxygen partial pressure and does not lose its insulating property, and as a result, a multilayer ceramic capacitor. However, it has a drawback that the practical dielectric property as described above cannot be obtained.

On the other hand, as a non-reducing dielectric ceramic composition that can be used as a laminated ceramic capacitor having internal electrodes such as nickel, barium titanate solid solution (Ba, Ca, Sr) TiO ₃ is a basic oxide (Ba, A non-reducing dielectric ceramic composition in which Ca, Sr) O is used in excess of the stoichiometric ratio with respect to TiO ₂ which is an acidic oxide and a base metal such as nickel can be used as an internal electrode is disclosed in Japanese Patent Publication No. 57-42588. It is proposed in the gazette and the like.

This is generally because, in the ABO ₃ type crystal, the A ion having 12 coordination with oxygen larger than the B ion is more stoichiometric than the B ion located at the center of the oxygen octahedral (perovskite) structure. It is known that when the amount is excessive, the crystal lattice strongly attracts oxygen atoms and is difficult to be reduced, and the invention described in the above publication is based on the deviation of the stoichiometric ratio, and the non-reducing property of the dielectric material. Is improved.

However, the dielectric ceramic composition described in the above publication has a drawback that the rate of change of the dielectric constant with temperature is large and the dielectric properties are deteriorated.

In addition, as a high-dielectric-constant dielectric ceramic composition with a small rate of change in permittivity with temperature, BaTiO ₃ was added to bismuth stannate [Bi ₂
O _{3) 3],} zirconium bismuth [Bi ₂ (ZrO _{3) 3]}
Bismuth compounds such as nickel zirconate [(NiZrO ₃ )] and magnesium zirconate [(Mg
ZrO ₃ )] is added. This is because the maximum value of the dielectric constant near the Curie point of BaTiO ₃ is lowered by the strong depressor effect of the bismuth compound or nickel zirconate or magnesium zirconate, and the temperature change rate of the dielectric constant is reduced. However, when a base metal such as nickel is used as an internal electrode and a dielectric material obtained by adding a bismuth-based compound or nickel zirconate or magnesium zirconate to BaTiO ₃ is co-fired below the equilibrium oxygen partial pressure of Ni / NiO, the dielectric is reduced. Therefore, the insulating property is not lost, and as a result, satisfactory dielectric properties cannot be obtained.

Furthermore, BaTiO ₃ as the Ni / dielectric be calcined near the equilibrium oxygen partial pressure of NiO own non-reducing temperature change rate is small in dielectric constant without being reduced high dielectric constant type dielectric ceramic composition -MnO- MgO
A system composition has been proposed in JP-A-57-71866.

This is because MnO and MgO have the effect of suppressing the reduction of BaTiO ₃ , and the dielectric is not reduced even when fired in the vicinity of the equilibrium oxygen partial pressure, and has sufficient insulating properties, and MgO is the bismuth-based compound. Since it has a depressor effect similar to the above, the temperature change rate of the dielectric constant is reduced. However, the dielectric porcelain composition described in the above publication has a low dielectric constant itself, and the amount of MgO added is increased to increase the EIA standard (Electrification).
(ronic Industries Association Standard) Dielectric constant temperature change rate (however, +25 ℃ in the range of -55 ℃ ~ +125 ℃) within ± 15%, the dielectric constant will be lower than 2200, practical It has a drawback that excellent dielectric characteristics cannot be obtained.

[Object of the Invention]

The present invention has been devised in view of the above-mentioned drawbacks, and its purpose is
In the composition of BaTiO ₃ , CaZrO ₃ and MnO, 1250 ℃ ～ 13
No reduction occurs when firing in an atmosphere with an oxygen partial pressure at 50 ° C. of 3 × 10 ⁻¹⁰ atm to 3 × 10 ⁻⁸ atm, and base metal powder particles such as nickel used as internal electrodes are not oxidized. It is fired as a metal film, has a high relative permittivity and excellent insulation, has a small temperature change rate of the permittivity over a wide temperature range, and has a small dielectric loss tangent. It is to provide a dielectric ceramic composition.

[Means for solving problems]

The non-reducing dielectric porcelain composition of the present invention is a three-component porcelain composition having a composition formula of (BaTiO ₃ ) _X · (CaZrO ₃ ) _Y · (MnO) _Z, which is shown below in FIG.
A, B, C, is characterized by comprising a composition within the range surrounded by each point, provided that X, Y, Z in the above composition formula
Represents the mole fraction and satisfies X + Y + Z = 100.

X Y Z A 96.0 1.5 2.5 B 88.5 1.5 10.0 C 85.5 4.5 10.0 D 93.0 4.5 2.5 The present invention is the same as the above-mentioned bismuth-based compound or nickel zirconate or magnesium zirconate by adding CaZrO ₃ and MnO to BaTiO ₃ at the same time. depressor effect is obtained, to lower the maximum value of the dielectric constant at the Curie point near the BaTiO _3, as well as reduce the temperature change of the dielectric constant, the addition of CaZrO ₃ and 3 × 10 ^-10 atm~3 × 10 ^- The semiconductor of the dielectric porcelain is obtained by recombining the donor level electron formed by the oxygen defect generated during firing under a low oxygen partial pressure of ⁸ atm with the acceptor level formed by adding MnO. It suppresses deterioration and maintains high insulation.

〔Example〕

Next, the present invention will be described based on examples. As a starting material
BaCO ₃ and TiO ₂ were solid-phase reacted at 1150 ℃ and CaCo ₃ and ZrO ₂ at 1220 ℃ to synthesize BaTiO ₃ and CaZrO ₃ and finely pulverized. Next, the synthetic fine powders BaTiO ₃ , CaZrO ₃ and MnCO ₃ were weighed so as to have the proportions shown in Table 1 and mixed with a dispersant and a dispersion medium in a ball mill to prepare a raw material slurry. Then, an organic binder was added to this raw material slurry together with a plasticizer, and the mixture was thoroughly stirred and degassed under vacuum, and then formed into a film by the doctor blade method. Next, 20 of the above films were stacked and thermocompression bonded by hot pressing, and the obtained plate-like sample (thickness 0.5 mm) was cut into a length of about 10 mm and a width of about 10 mm. The oxygen partial pressure of this sample is 3 × 10 ^-10 atm
It is controlled to 3 × 10 ^-8 atm and the carrier gas is N ₂ gas 125
Firing was performed at 0 ° C to 1350 ° C for 2 hours. An indium-gallium (In-Ga alloy) was applied to both upper and lower surfaces of the finally obtained fired body.

And after leaving these evaluation samples at room temperature for 48 hours,
The capacitance and dielectric loss tangent were measured at a frequency of 1.00 KHz and an input signal level of 1.0 Vrms, and the relative permittivity was calculated from the capacitance. After that, DC 50V was applied for 1 minute, and the insulation resistance at that time was measured. Also, in the temperature range of -55 ° C to + 125 ° C, the capacitance and the dielectric loss tangent were measured under the same conditions as above, and the rate of change of the capacitance at each temperature with respect to the capacitance at + 25 ° C was calculated. .

The above results are shown in Table 1. However, the insulation resistance in the table is the product of the capacitance (C, μF) and the insulation resistance (R, MΩ) (C ・ R, M
Ω · μF).

As is clear from Table 1, sample Nos. 1, 2, ₃ , and 4 are when the CaZrO ₃ mole fraction is less than 15, and the depressor effect works even if the MnO mole fraction is 2.5 or more at the same time. However, the temperature change rate of the relative permittivity exceeds ± 15% and deviates from the EIA standard, and the insulation resistance is extremely low at 890 MΩ · μF or less, and the relative permittivity is also small at 2547 or less. When the molar fraction of CaZrO ₃ exceeds 4.5, as shown in sample numbers 37, 38, 39, 40, and when the molar fraction of MnO is less than 2.5, as shown in sample numbers 5, 20, 30. However, the above-mentioned temperature change rate of relative permittivity exceeds ± 15%, which is outside the EIA standard. In addition, sample numbers 12 and 36, when the addition amount of MnO exceeds 10.0 in mole fraction, the relative dielectric constant is 2490 or less,
None of them have practical dielectric properties.

On the other hand, the dielectric ceramic composition within the scope of the claims of the present invention has a sufficiently large relative permittivity of 2591 to 3347 and an insulation resistance of C.
R is as large as 1016 to 2733 MΩ · μF, and the rate of change in the relative permittivity with temperature is within ± 15%, and all of them have excellent electric charge characteristics.

〔The invention's effect〕

The dielectric porcelain composition within the scope of the present invention surrounded by each point of ABCD in FIG. 1 has any of the temperature characteristics of relative permittivity, dielectric loss tangent tan δ, insulation resistance C · R, and relative permittivity. It is satisfactory.

Further, in the present invention, the firing temperature is in the range of 1250 ℃ ~ 1350 ℃, the firing condition of oxygen partial pressure is equal to or less than the equilibrium oxygen partial pressure of Ni / NiO, the dielectric porcelain can be sintered simultaneously with the nickel metal electrode. In addition, since it satisfies all the dielectric characteristics of sintered porcelain and also sinters nickel metal fine particles as a metal film without being oxidized, it can be used as a dielectric porcelain of a laminated porcelain capacitor with nickel as an internal electrode. It is understood that it is sufficiently practical.

[Brief description of drawings]

FIG. 1 is a ternary diagram showing the composition range of the non-reducing dielectric ceramic composition of the present invention.

Claims (1)

[Claims] 1. A ternary porcelain composition having a composition formula of (BaTiO ₃ ) _X. (CaZrO ₃ ) _Y. (MnO) _Z, which is shown below in FIG.
A non-reducing dielectric ceramic composition having a composition within a range surrounded by points A, B, C, and D. However, in the above composition formula, X, Y and Z represent mole fractions and satisfy X + Y + Z = 100. XYZ A 96.0 1.5 2.5 B 88.5 1.5 10.0 C 85.5 4.5 10.0 D 93.0 4.5 2.5