JP3250932B2 - Non-reducing dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic capacitor, and more particularly to a non-reducing dielectric ceramic composition for a laminated ceramic capacitor having internal electrodes mainly composed of nickel (Ni).

[0002]

2. Description of the Related Art Conventionally, multilayer ceramic capacitors are generally
Sheet-shaped BaT with internal electrodes printed on its surface
It is formed by laminating a plurality of dielectrics mainly composed of iO ₃ , connecting the internal electrodes of each sheet alternately and in parallel to a pair of external connection electrodes, and sintering and integrating them. Such multilayer ceramic capacitors have been widely used in various electronic circuits of electronic components whose miniaturization progresses rapidly with the development of electronics in recent years.

[0003] Such a conventional dielectric material containing BaTiO ₃ as a main component must be sintered at a high temperature of 1250 ° C to 1350 ° C. When this material is used as a dielectric of a laminated ceramic capacitor, an internal electrode is formed. It is necessary to use palladium (melting point: 1555 ° C.), which is an expensive noble metal that does not melt and does not oxidize at the sintering temperature of the dielectric, or an alloy thereof. There has been a problem that the number of components of the internal electrodes becomes large and the cost increases.

Therefore, the conventional multilayer ceramic capacitor is
Despite high volumetric efficiency, excellent dielectric properties, and high reliability, price has been a major obstacle to its development.

Therefore, it has been attempted to use an inexpensive base metal such as nickel (Ni) as the internal electrode. However, if the base metal is used as the internal electrode, a dielectric made of barium titanate (BaTiO ₃ ) or the like is used. When the base metal and the base metal internal electrode are simultaneously sintered, the condition that the base metal can be sintered as a metal film without being oxidized is that the parallel oxygen partial pressure of Ni / NiO is about 0.03 Pa at 1300 ° C. The oxygen partial pressure must be as follows. In this case, the dielectric composed of BaTiO ₃ or a solid solution thereof is generally reduced under the oxygen partial pressure and loses its insulating property. However, it has a drawback that it is not possible to obtain excellent dielectric properties.

Therefore, a basic oxide (Ba, Ca, Sr) is used as a non-reducing dielectric ceramic composition for a multilayer ceramic capacitor having an internal electrode such as nickel (Ni).
Barium titanate solid solution (Ba, Ca, S) in which O is added in excess of stoichiometric ratio to TiO ₂ as an acidic oxide
r) Non-reducing dielectric ceramic compositions comprising TiO ₃ have been proposed in Japanese Patent Publication No. 57-42588.

[0007]

Generally, an ABO ₃ type crystal has an A ion which has a coordination of 12 atoms with oxygen, which is larger than B ion, with respect to a B ion located at the center of an oxygen octahedral (perovskite) structure. When the stoichiometric ratio is in excess of the stoichiometric ratio, it is known that the crystal lattice strongly attracts oxygen atoms and is difficult to be reduced, and the non-reducing dielectric ceramic composition is based on this stoichiometric deviation. However, although the non-reducing property of the dielectric is improved, there is a problem that the temperature change rate of the dielectric constant is large and the dielectric characteristics are deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object the purpose of firing even in an atmosphere at an oxygen partial pressure of 3 × 10 ^{−8 to} 3 × 10 ⁻³ Pa at 1150 ° C. to 1250 ° C. Not reduced, and base metal powder particles such as nickel (Ni) used as an internal electrode are sintered as a metal film without being oxidized, and have a high relative dielectric constant, excellent insulating properties, and a change in dielectric constant with temperature. An object of the present invention is to provide a highly economical non-reducing dielectric ceramic composition having a low modulus over a wide temperature range and a small dielectric loss tangent.

[0009]

The non-reducing dielectric ceramic composition of the present invention comprises at least Ba, Ti,
A composite oxide containing Mg, Mn, Y, Li, and Si, wherein a composition formula based on a molar ratio of Ba, Mg, and Mn among the metal elements is 100 BaTiO ₃ + xMgO + yMn.
When represented by O, x and y representing a molar ratio to 100 mol of BaTiO ₃ are 0.50 ≦ x ≦ 8.00, 0.05
With respect to the main component represented by ≦ y ≦ 0.50, the composition formula based on the molar ratio of Y, Li, and Si among the metal elements is represented by aY _{2
O 3 + bLi 2 O + cSiO} 2 and when expressed, a representative of the molar ratio, b and c are 10 ≦ a ≦ 60,10 ≦ b ≦ 60,3
After calcination, an additive represented by 0 ≦ c ≦ 80 and a + b + c = 100 is contained in an amount of 1 to 4% by weight with respect to the main component, the insulation resistance is 1000 MΩ · μF or more, and the aging rate is 1.5%. It is characterized by the following. Further, the non-reducing dielectric ceramic composition of the present invention is a composite oxide containing at least Ba, Ti, Mg, Mn, Y, B and Si as metal elements, and among the metal elements, Ba,
The composition formula based on the molar ratio of Mg and Mn is 100 BaTiO ₃
+ XMgO + yMnO, BaTiO ₃ 1
X and y representing the molar ratio with respect to 00 mol are 0.50 ≦ x ≦
With respect to the main component represented by 8.00 and 0.05 ≦ y ≦ 0.50, the composition formula based on the molar ratio of Y, B, and Si among the metal elements is represented by aY ₂ O ₃ + bB ₂ O ₃ + cSiO _2. When a, b and c representing the molar ratio are 10 ≦ a ≦ 60,
The additive represented by ≦ b ≦ 60, 30 ≦ c ≦ 80, and a + b + c = 100 was calcined and then contained in an amount of 1 to 4% by weight based on the main component.

The composition formula based on the molar ratio of the main component is represented by 10
When expressed as 0BaTiO ₃ + xMgO + yMnO,
The molar ratio x of MgO to 100 moles of BaTiO ₃ is
When 0.50 ≦ x ≦ 8.00, the insulation resistance is low when x is smaller than 0.50, and when x is larger than 8.0, the dielectric constant is small and the insulation resistance is small. X is more preferably 1.0 to 2.0.

In addition, M per 100 moles of BaTiO ₃
The reason why the molar ratio y of nO is 0.05 ≦ y ≦ 0.50 is that when y is smaller than 0.05, the insulation resistance is low,
This is because when y is larger than 0.50, the aging rate increases, and y is more preferably 0.1 to 0.2.

On the other hand, the composition formula based on the molar ratio of the additive is represented by aY ₂ O ₃ + bLi ₂ O + cSiO ₂ (a + b + c
= 100), the molar ratio a of Y ₂ O ₃ is 10
The reason for setting ≦ a ≦ 60 is that when a is smaller than 10, the insulation resistance is low, and when a is larger than 60, the relative dielectric constant is reduced, the sinterability is reduced, and the insulation resistance is also low. And a is more preferably 20 to 40.

The reason why the molar ratio b of Li ₂ O or B ₂ O ₃ is set to 10 ≦ a ≦ 60 is that when b is smaller than 10, the temperature characteristic of the capacity is deteriorated and b is larger than 60. In this case, the relative dielectric constant becomes small, and b is 2
0 to 40 is more desirable.

Further, the molar ratio c of SiO ₂ is set so that 30 ≦ a ≦
The reason for setting the value to 80 is that when c is smaller than 30, the sinterability is reduced, and when c is larger than 80, the relative dielectric constant is reduced.

Further, the content of the additive is 1 to 4% by weight.
The reason for this is that when the content is less than 1% by weight, the sinterability decreases, and when the content is more than 4% by weight, the relative dielectric constant decreases. 1.5 to 2.5% by weight is more desirable.

In the present invention, the average crystal grain size of BaTiO ₃ is desirably 1.5 μm or less. this is,
This is because when the average crystal grain size of BaTiO ₃ is larger than 1.5 μm, the insulation resistance tends to decrease, and the absolute value of the temperature change rate of the capacitance tends to increase.

It is desirable that the product of the particle diameter of BaTiO ₃ and the specific surface area is 1.2 or less, and if it exceeds 1.2, the insulation resistance tends to decrease.

The non-reducing dielectric ceramic composition of the present invention is obtained by the following procedure. First, BaCO ₃ powder, Ti
After mixing the O ₂ powder, a solid phase reaction
An iO ₃ powder is synthesized and pulverized to a particle size of 1.5 μm or less.

Next, Y ₂ O ₃ powder, SiO ₂ powder, L
The i ₂ CO ₃ powder or the B ₂ O ₃ powder is weighed to a predetermined ratio, mixed and then calcined at a predetermined temperature to obtain an additive.

Next, the above-mentioned synthetic fine powder BaTiO ₃ ,
The additives are weighed to MnCO ₃ powder and MgO powder so as to have a predetermined ratio, and mixed with a dispersant and a dispersion medium in a ball mill to prepare a raw material slurry. Then, add an organic binder and a plasticizer to this slurry,
After sufficient stirring, the mixture is formed into a film by a doctor blade method. After the obtained films are stacked and thermocompression bonded, they are cut into a predetermined shape. Finally, the molded body is controlled at an oxygen partial pressure of 3 × 10 ^{−8 to} 3 × 10 ⁻³ Pa, and in an atmosphere in which a carrier gas is nitrogen gas, at 1150 to 1250 ° C.
At a temperature of

[0021]

According to the non-reducing dielectric ceramic composition of the present invention,
MnO and MgO form an acceptor level. By adding these, 3 × 10 ^{−8 to} 3 × 10
Donor level electrons formed by oxygen defects generated when firing under a low oxygen partial pressure of ^-3 Pa are MnO and Mg.
Recombination takes place at the acceptor level formed by the addition of O, which suppresses the formation of the dielectric ceramic into a semiconductor and maintains high insulating properties.

In addition, Y ₂ O ₃ , SiO ₂ , Li ₂ O or B ₂ O ₃ act as a sintering aid and also exist as a grain boundary component to improve the reduction resistance and reliability of the porcelain.

On the other hand, since the aging characteristic is proportional to the amount of MnO, a dielectric ceramic composition having a small aging rate can be obtained by limiting the amount of MnO.

[0024]

EXAMPLES Hereinafter, the non-reducing dielectric ceramic composition of the present invention will be described in detail based on examples. First, BaCO ₃ powder having a purity of 99% or more and TiO ₂ powder are mixed as starting materials, and then solid-phase reaction is performed at a temperature of 1150 ° C. to form BaT.
iO ₃ powder was synthesized and pulverized to a particle size of 1.5 μm or less.

Next, a Y ₂ O ₃ powder and a SiO ₂ powder, and further a Li ₂ CO ₃ powder or a B ₂ O ₃ powder are shown in Tables 1 and 2.
, And then calcined at a temperature of 1000 ° C. to produce an additive.

Thereafter, the synthetic fine powder Ba as the main component is
TiO ₃ and MnCO ₃ powder, the MgCO ₃ powder, the weighed additive to respective concentrations on the percentage of Tables 1 and 2, known dispersing agent, is mixed in a ball mill together with a dispersion medium to prepare a raw material slurry .

[0027]

[Table 1]

[0028]

[Table 2]

Next, an organic binder and a plasticizer were added to the raw material slurry, and the mixture was sufficiently stirred, formed into a film shape by a doctor blade method, stacked and thermocompressed, cut, and cut to a length of 10 mm. 10 mm wide,
A laminate having a thickness of 0.5 mm was produced.

Thereafter, the laminate is subjected to an oxygen partial pressure of 3 × 10
^{-8 to} 3 × 10 ⁻³ Pa, and calcined at a temperature of 1150 to 1250 ° C. for 2 hours using nitrogen as a carrier gas. In the upper and lower surfaces of the thus obtained sintered body, In
An electrode for measuring electrical characteristics was formed by applying a -Ga alloy to prepare an evaluation sample.

Next, after leaving the evaluation sample at room temperature for 48 hours, a frequency of 1.0 kHz and an input signal level of 1.0
The capacitance and the dielectric loss tangent were measured at Vrms, and the relative permittivity was calculated from the capacitance. Then, 50V DC is
Min, and the insulation resistance at that time was measured.

In the temperature range of -55 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. Calculated.

Further, after the above-mentioned evaluation sample was heat-treated at 150 ° C. for 1 hour, it was left at 25 ° C., and a change rate (aging rate) of the capacitance after 10 hours with respect to the capacitance after 1 hour was calculated. However, the insulation resistance is the capacitance C (μF)
It was expressed by the product CR (MΩ · μF) of the resistance and the insulation resistance R (MΩ).

[0034]

[Table 3]

[0035]

[Table 4]

As is clear from Tables 3 and 4, Sample Nos. 14, 15, and 4 containing less than 1% by weight of the additive were used.
In Sample Nos. 6 and 47, the sinterability is reduced and the insulation resistance is low. Conversely, in Samples 20 and 52 exceeding 4% by weight, the relative dielectric constant tends to be low and the insulation resistance is low.

Sample Nos. 21, 26, 53 and 58 in which the molar ratio a of Y ₂ O ₃ is smaller than 10 have lower insulation resistance, and Sample Nos. 24 and 56 in which a is larger than 60 have a relative dielectric constant of Smaller and the insulation resistance is lower.

Further, in Sample Nos. 22 and 54 in which the molar ratio b of Li ₂ O or B ₂ O ₃ is smaller than 10, the temperature characteristic of the relative dielectric constant is poor, and in Sample No. 25 in which b is larger than 60,
In No. 57, the insulation resistance is low and the temperature characteristics are poor.

Sample Nos. 23, 24, 25, 55, 56 and 57 in which the molar ratio c of SiO ₂ is smaller than 30 have lower sinterability, lower insulation resistance, and Sample No. 26 in which c is larger than 80. , 58 have small relative dielectric constants.

On the other hand, Sample Nos. 1 and 33 in which the amount of MgO is less than 0.5 mol% have low insulation resistance, and Sample Nos. 6 and 38 in which MgO content exceeds 8 mol% have low dielectric constants. Also, M
In Sample Nos. 8 and 40 in which the nO content was less than 0.05 mol%, the insulation resistance was low, and in Sample Nos.
At 45, the aging rate is large.

In contrast to the above comparative examples, the samples of the present invention all have a relative dielectric constant of 2500 or more and a dielectric loss tangent (tan δ).
Of 2.5% or less, an insulation resistance of 1000 MΩ · μF, a temperature change rate of a relative dielectric constant of ± 15% or less, and an aging rate of 1.5% or less.

The non-reducing dielectric ceramic composition of the present invention is not limited to the above-described embodiment.

[0043]

As described above, the non-reducing dielectric ceramic composition of the present invention has a firing temperature in the range of 1150 to 1250 ° C. and an oxygen partial pressure of not more than the parallel oxygen partial pressure of Ni / NiO. Even when calcined, it shows excellent characteristics in temperature characteristics such as relative dielectric constant, dielectric loss tangent, insulation resistance, relative dielectric constant, and aging rate of capacitance. This is a non-reducing dielectric ceramic composition excellent in practicality and suitable for use in a laminated ceramic capacitor using an internal electrode as a main component.

Continuation of the front page (72) Inventor Nobuyoshi Fujikawa 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Examiner at Kyocera Research Institute Tatsuo Takeshige (56) References JP-A-4-264305 (JP, A) JP-A Sho 63-151658 (JP, A)

Claims (2)

(57) [Claims] At least Ba, Ti, M as a metal element
g, Mn, Y, a composite oxide containing Li and Si, among the metal elements, when expressed Ba, Mg, the composition formula by molar ratio of Mn and 100BaTiO ₃ + xMgO + yMnO, for BaTiO ₃ 100 moles With respect to a main component in which x and y representing a molar ratio are represented by 0.50 ≦ x ≦ 8.00 0.05 ≦ y ≦ 0.50, a molar ratio of Y, Li, and Si among the metal elements is determined. when the composition formula represented as _{aY 2 O 3 + bLi 2 O} + cSiO 2, a representative of a molar ratio, b and c are 10 ≦ a ≦ 60 10 ≦ b ≦ 60 30 ≦ c ≦ 80 a + b + c = 100 additive represented by After calcination, 1-4
Weight%, insulation resistance is 1000MΩ ・ μF
As described above, the non-reducing dielectric ceramic composition has an aging rate of 1.5% or less. 2. At least Ba, Ti, M as a metal element
g, Mn, Y, a composite oxide containing B and Si, among the metal elements, when expressed Ba, Mg, the composition formula by molar ratio of Mn and 100BaTiO ₃ + xMgO + yMnO, for BaTiO ₃ 100 moles With respect to a main component in which x and y representing a molar ratio are represented by 0.50 ≦ x ≦ 8.00 0.05 ≦ y ≦ 0.50, a molar ratio of Y, B, and Si among the metal elements is determined. when the composition formula represented as _{aY 2 O 3 + bB 2 O} 3 + cSiO 2, a representative of a molar ratio, b and c are shown in 10 ≦ a ≦ 60 10 ≦ b ≦ 60 30 ≦ c ≦ 80 a + b + c = 100 added After calcination of the product, 1 to 4
A non-reducible dielectric porcelain composition, characterized in that it is contained by weight.