JPH05194027A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To obtain a ceramic composition sinterable at relatively low temperatures, having high reliability, good temperature characteristics and high dielectric constant by incorporating a specific composition consisting mainly of barium titanate with each specified amount of zirconate like lead zirconate, stannate and specific titanate. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100mol of a dielectric composition comprising (1) 68.3-97.89mol% of BaTiO3, (2) 1-20mo1% of PbZrO3, (3) 0.6-3mol% of Cub, (4) 0.2-4mol% of ZnO, (5) 0.01-0.7mol% of Mn2O3, and (6) 0.3-4mol% of a rare earth metal oxide with (B) 1-20mol of at least one kind selected from zirconates except PbZrO3, stannates and titanates except BaTiO3. With addition of PbZrO3, the composition becomes highly flat in temperature characteristics, satisfying the F- characteristics in the JIS standard, realizing high dielectric constant, and being sinterable at temperatures as low as <=1200 deg.C. Furthermore, addition of at least one kind selected from zirconates except PbZrO3, stannates and titanates maintains the F-characteristics for the temperature characteristics as well as realizes a dielectric constant of >=20000 at ca.room temperature.

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 containing barium titanate as a main component, and more particularly to a ferroelectric composition suitable for use as a capacitor.

[0002]

2. Description of the Related Art Conventionally, a ferroelectric ceramic composition containing barium titanate as a main component has a sintering temperature of 1300 ° C.
Since it is extremely high as described above, a noble metal having a high melting point capable of withstanding a high sintering temperature, such as platinum, palladium, or gold, is used as an internal electrode material when it is used as a laminated capacitor. Since these noble metals are expensive, the cost of the multilayer capacitor is also high. Further, since the sintering is performed at a high temperature, the design of the sintering furnace, the energy required for sintering, etc. also become a problem. That is, when manufacturing a multilayer capacitor, from the viewpoint of cost, it is preferable to use inexpensive silver as a main component as the internal electrode material, and
Ferroelectric ceramic compositions that can be sintered at low temperatures are strongly desired because of the ease of furnace design.

In Japanese Patent Laid-Open No. 1-201069, by adding a specific amount of zinc oxide, manganese oxide, a rare earth oxide, and copper oxide to barium titanate, it is possible to sinter at a temperature of 1200.degree. Uniformity, good electrical characteristics (eg, dielectric constant, insulation resistance, dielectric loss) and at the same time satisfying reliability, and addition of barium stannate and calcium stannate in specific amounts impairs the above characteristics However, it is disclosed that the dielectric constant near room temperature increases to 12,000 or more. However, the dielectric ceramics obtained by this method have poor temperature characteristics of capacitance (temperature dependence of capacitance change rate). For example, if the temperature characteristics are adapted to JIS standards, high capacitance cannot be obtained, and practical use is impossible. Becomes a serious problem. In addition, in recent years, with the increase in capacity and size of multilayer ceramic capacitors, there has been a demand for a dielectric ceramic composition having a higher dielectric constant.

[0004]

DISCLOSURE OF THE INVENTION According to the present invention, a dielectric ceramic which can be sintered at a temperature of 1200 ° C. or less, has a uniform grain and high reliability, and at the same time has a good temperature characteristic and an even higher dielectric constant. It is intended to provide a composition.

[0005]

As a result of extensive studies, the present inventors have found that barium titanate, lead zirconate, copper oxide,
1200 ° C or less when a specific amount of one or more selected from zirconate, stannate, and titanate is added to a composition containing zinc oxide, manganese oxide, and a rare earth oxide as a main component The inventors have found that the sintering can be performed at the above temperature, the temperature characteristics can be flattened, and at the same time, the dielectric constant near room temperature can be dramatically improved, and the present invention has been achieved.

That is, the present invention provides 6 as the first component.
8.3 to 97.89 mol% barium titanate, 1 to 20 mol% lead zirconate as the second component, 0.6 to 3 mol% copper oxide as the third component, and 0.2 to 4 mol% as the fourth component. Zinc oxide, 0.0 as the fifth component
To 100 mol of the dielectric ceramic composition consisting of 1 to 0.7 mol% of manganese oxide and 0.3 to 4 mol% of a rare earth oxide as the sixth component, as the seventh component, zirconate, stannate, titanic acid The present invention relates to a dielectric ceramic composition containing 1 to 20 mol of one or more kinds selected from salts.

The dielectric ceramic composition to which lead zirconate is added as the second component of the present invention has an extremely flat temperature characteristic as compared with the case where it is not added, and the JIS standard F characteristic (at −25 to + 85 ° C.). Capacity change rate +30 ~ in temperature range
(At less than -80%) and 160 at room temperature
A high dielectric constant of 00 or more can be obtained. Furthermore, the temperature characteristics can be controlled easily by the amount of lead zirconate added, and the temperature characteristics are flattened to satisfy the JIS standard E characteristics (capacity change rate within +20 to -55% within the temperature range of -25 to + 85 ° C). Even if it is made, the dielectric constant near room temperature can be maintained at 8000 or more. The dielectric constant in each of these characteristics is extremely higher than in the past, and it is possible to sinter at a low temperature of 1200 ° C. or less.
Further, when barium zirconate is added in a specific amount as the seventh component, the temperature characteristic maintains the F characteristic, and at the same time, a dielectric constant of 20,000 or more is obtained near room temperature.

The proportion of barium titanate in the ceramic composition of the present invention is in the range of 68.3 to 97.89 mol%. 1 when the ratio is more than 97.89 mol%
Sintering becomes difficult at a temperature of 200 ° C or lower, and 68.3mo
If it is less than 1%, significant deformation of the base material occurs during sintering.
The proportion of lead zirconate is 1-2 in the form of PbZrO _3.
It is in the range of 0 mol%. If the amount is less than 1 mol%, the effect of addition is not so remarkable and the temperature characteristic of the dielectric constant is not flat. Further, when it is 20 mol or more, the dielectric constant is remarkably lowered.

The proportion of copper oxide is 0.6 to 3 m as CuO.
It is in the range of ol%. When it is more than 3 mol%, delamination is remarkable and the value of dielectric loss becomes large. Further, the grain size at the time of sintering becomes nonuniform and large, and reliability is extremely deteriorated. When it is less than 0.6 mol%, low temperature sintering becomes difficult. The proportion of zinc oxide is in the range of 0.2 to 4 mol% in the form of ZnO. If it exceeds 4 mol%, it becomes difficult to sinter at 1200 ° C. or less, resulting in non-uniformity of grains and reduction in insulation resistance. 0.2 mol%
If it is less than the above, the effect of addition is hardly recognized, and the dielectric loss increases.

The proportion of manganese oxide in the form of Mn ₂ O ₃ is in the range 0.01 to 0.7 mol%. 0.7m
When it is more than ol%, it is difficult to sinter at 1200 ° C. or less, and when manufacturing a multilayer capacitor, delamination between the internal electrode and the dielectric layer is remarkable. Also, 0.01
If it is less than mol%, almost no effect of addition is recognized, and the reliability is low.

Rare earth oxide RE _m O _n (RE = La, C
e, Nd, Sm, Gd, Dy, Ho, Er, Tm, etc.)
Is in the range of 0.3 to 4 mol% as RE. The reliability improves as the amount of addition increases, but 4 mol
If it exceeds%, the microstructure tends to be nonuniform and grain growth is also observed. If it is further increased, it becomes difficult to sinter at 1200 ° C or lower. If it is 0.3 mol% or less, the effect of addition is hardly recognized and the reliability is low.

The proportion of one or more oxides selected from zirconates excluding lead zirconate as the seventh component, stannates, and titanates excluding barium titanate is as follows. It is in the range of 1 to 20 mol based on 100 mol of the sum of the second component, the third component, the fourth component, the fifth component and the sixth component. If the amount is less than 1 mol, the effect of addition is not so remarkable and the dielectric constant near room temperature is low. In addition, 20m
If it is ol or more, sintering at 1200 ° C. or less becomes difficult.

The barium titanate used in the present invention may be produced by any method such as a solid phase method and a liquid phase method (eg, oxalate method, alkoxide method). Average particle size is 1 μm
When a material having a small particle size and a uniform particle size distribution is used, it is possible to obtain a highly reliable ceramic dielectric having a more uniform microstructure and good electric characteristics. In the present invention, as the copper oxide, monovalent, divalent, and monovalent and divalent coexisting ones can be used. As manganese oxide, any of divalent, trivalent, tetravalent, heptavalent and those in which they coexist can be used. As the rare earth oxide, any of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, dysprosium oxide, holmium oxide, erbium oxide and thulium oxide can be used.

Barium zirconate, potassium zirconate and the like are used as the zirconate salts excluding lead zirconate as the seventh component, and barium stannate and calcium stannate are used as the stannate salts, and titanate other than barium titanate are used. Preferred examples thereof include strontium titanate, calcium titanate, magnesium titanate, and the like. Also,
The second component and the oxide added as the seventh component in the present invention, in the form of a usual complex oxide of zirconate, stannate, and titanate, and the single oxides and the constituents thereof. It is also possible to add mixed oxides. As the oxide, any inorganic acid salt such as hydroxide or carbonate, or organic salt such as oxalate or alkoxide may be used as long as it decomposes to an oxide at a temperature equal to or lower than the sintering temperature.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples.

[0016]

Examples 1-4 and Comparative Examples 1-2 Barium titanate, lead zirconate, copper oxide, zinc oxide, manganese oxide,
Table 1 shows samarium oxide, barium stannate, calcium stannate, and barium zirconate as rare earth oxides.
Accurately weighed so as to have the ratio shown in Table 1, pure water was added, and the mixture was mixed by a wet ball mill. After sufficiently drying and roughly crushing the mixture, a paste was prepared by using acrylic resin as a binder, trichloroethane as a solvent, and zirconia as a ball medium. A green sheet having a thickness of 20 μm was prepared from the obtained paste by the doctor blade method, and a laminated capacitor having 50 effective layers was manufactured as a prototype by the screen printing method. The material of Ag / Pd = 70/30 was used as the internal electrode. After debinding this chip, 1
It sintered at 100 degreeC for 6 hours. Next, a silver electrode was baked as an external electrode and the electrical characteristics were measured.

The permittivity was measured using an LCR meter [AG-4304 manufactured by Ando Electric Co., Ltd.] at 1 KHz, 1 V and 2
The capacitance measured under the condition of 0 ° C. and the cross section of the multilayer capacitor were polished, and calculated from the dielectric thickness and the effective internal electrode area obtained by taking an optical micrograph. Temperature characteristics are JI
According to the S standard, the capacitance at 20 ° C is used as a reference -25
It was determined as the rate of change in capacitance at ° C and + 85 ° C. In addition, a high temperature load test was performed to evaluate reliability, and the life was 1
The time required to reach a failure rate of 63% under conditions of 55 ° C. and 100 VDC load was expressed.

The measurement results are shown in Table 2. 1 in Comparative Example 1
Although a dielectric constant of 4000 or more can be obtained, the temperature dependence of the capacitance change rate is large, and the F characteristic of JIS standard is not satisfied at + 85 ° C. Further, in Comparative Example 2 having improved temperature characteristics, a high dielectric constant cannot be obtained. On the other hand, in Examples 1 to 4 in which lead zirconate was added, the temperature characteristics became flat and at the same time, a dielectric constant of 16000 or more was obtained. Furthermore, in Example 2 in which a specific amount of lead zirconate and barium zirconate are combined, the temperature characteristics satisfy the F characteristics,
Moreover, a dielectric constant of 20,000 or more is obtained. In addition, the temperature characteristic is further flattened by the addition amount of lead zirconate, and E
Even in Example 4 satisfying the characteristics, the dielectric constant was 8000.
Keep above. For reliability, 155 ℃, 100
It can be seen that a multilayer capacitor having a long life and a high reliability can be obtained under the VDC load condition.

In the above examples, barium titanate having a molar ratio of Ba and Ti of about 1 was used.
Good characteristics can be obtained even if the ratio is shifted by about 0.05 mol.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

As described above, the ferroelectric ceramic composition of the present invention can be sintered at a temperature of 1200 ° C. or less, has a flat temperature characteristic and a high dielectric constant of 16000 or more near room temperature. , High reliability. In addition, it is easy to control the temperature characteristics. Therefore, when a monolithic ceramic capacitor is produced using the ferroelectric ceramic composition of the present invention, it is easy to design a product conforming to the capacitor standard such as EIAJ, and a small-sized, high-capacity and highly reliable laminated Ceramic capacitors can be obtained at low cost.

These are extremely useful as a dielectric composition for a laminated ceramic capacitor and have great industrial value.

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[Procedure amendment]

[Submission date] February 19, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Barium zirconate, calcium zirconate and the like are used as zirconates excluding lead zirconate as the seventh component, and barium stannate, calcium stannate and the like are used as stannates and barium titanate. Preferred examples of the titanate to be removed include strontium titanate, calcium titanate and magnesium titanate. Further, in the second component and the oxide added as the seventh component in the present invention, zirconates, stannates, titanates in the form of ordinary complex oxides, and the single oxidation constituting them It is also possible to add a substance and / or a complex oxide by mixing. For the oxide, hydroxide,
Inorganic acid salts such as carbonates, organic salts such as oxalates and alkoxides, and the like can be used as long as they decompose to oxides at a temperature below the sintering temperature.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

Examples 1-4 and Comparative Examples 1-2 Barium titanate, lead zirconate, copper oxide, zinc oxide, manganese oxide,
Samarium oxide as a rare earth oxide, and barium stannate, calcium stannate, barium zirconate, titanate
Strontium acidate was accurately weighed so that the ratio shown in Table 1 was obtained, pure water was added, and the mixture was mixed by a wet ball mill. After sufficiently drying and roughly crushing the mixture, a paste was prepared by using acrylic resin as a binder, trichloroethane as a solvent, and zirconia as a ball medium. A green sheet having a thickness of 20 μm was prepared from the obtained paste by a doctor blade method, and a laminated capacitor having 50 effective layers was manufactured by a screen printing method. The material of Ag / Pd = 70/30 was used as the internal electrode. After debinding the chip, it was sintered at 1100 ° C. for 6 hours. Next, a silver electrode was baked as an external electrode and the electrical characteristics were measured.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The measurement results are shown in Table 2. 1 in Comparative Example 1
Although a dielectric constant of 4000 or more can be obtained, the temperature dependence of the capacitance change rate is large, and the F characteristic of JIS standard is not satisfied at + 85 ° C. Further, in Comparative Example 2 having improved temperature characteristics, a high dielectric constant cannot be obtained. On the other hand, in Examples 1 to 4 in which lead zirconate was added, the temperature characteristics became flat and at the same time, a dielectric constant of 16000 or more was obtained. Further, in Example 3 in which a specific amount of lead zirconate and barium zirconate are combined, the temperature characteristics satisfy the F characteristics,
Moreover, a dielectric constant of 20,000 or more is obtained. In addition, the temperature characteristic is further flattened by the addition amount of lead zirconate, and E
Also in Example 5 satisfying the characteristics, the dielectric constant was 8000.
Keep above. For reliability, 155 ℃, 100
It can be seen that a multilayer capacitor having a long life and a high reliability can be obtained under the VDC load condition.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

As described above, the ferroelectric ceramic composition of the present invention can be sintered at a temperature of 1200 ° C. or less, has a flat temperature characteristic and a high dielectric constant of 16000 or more near room temperature. , High reliability. In addition, it is easy to control the temperature characteristics. Therefore, when a laminated ceramic capacitor is prepared using the ferroelectric ceramic composition of the present invention, it is easy to design a product that conforms to the capacitor standard such as JIS , and is a small-sized, high-capacity, highly reliable laminated Ceramic capacitors can be obtained at low cost.

Claims (1)

[Claims] 1. A first component of 68.3 to 97.89 m
ol% barium titanate, 1 to 20 m as the second component
ol% lead zirconate, 0.6-3m as the third component
ol% copper oxide, 0.2 to 4 mol% zinc oxide as the fourth component, 0.01 to 0.7 mol% manganese oxide as the fifth component, 0.3 to 4 mol% rare earth oxide as the sixth component Dielectric ceramic composition consisting of 100mo
Dielectric ceramic composition containing 1 to 20 mol of at least one selected from zirconates excluding lead zirconate, stannates, and titanates excluding barium titanate as a seventh component with respect to 1.