JPH06104587B2 - Dielectric ceramic composition and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dielectric ceramic composition suitable for use as a barium titanate-based capacitor, and a method for producing the same.

(Prior Art) Conventionally, barium titanate and compositions obtained by blending barium titanate with shifters, depressors, etc.
Sintered at a high temperature of 1400 ℃ and used as a capacitor. However, when sintered at such a high temperature, it causes wear of expensive setters such as zirconia and the sintering furnace, and a large amount of energy is required for sintering, resulting in a capacitor and an expensive capacitor. Become. Furthermore, in order to manufacture a laminated capacitor using a conventional composition, it is necessary to use an expensive noble metal such as platinum or palladium that can withstand a high sintering temperature as an internal electrode material. Multilayer capacitors are extremely expensive. Therefore, it is possible to reduce the wear of the setter and the sintering furnace, and to use an inexpensive internal electrode containing silver as a main component when manufacturing a multilayer capacitor. Things are strongly desired.

Copper oxide is known as one of the sintering aids that can lower the sintering temperature of barium titanate. By adding 0.5 mol% or less cupric oxide to barium titanate,
It is shown in Trans.Brit.Ceram.Soc., 74 , 165, (1975) that a sintered body having a theoretical density can be obtained at a sintering temperature of ° C.

JP-A-53-8200, CuO-Cu ₂ O in Purobesukaito oxide
Forming a eutectic mixture or CuO-Cu ₂ O / Me ^IV O ₂ eutectic mixture (however, Me ^IV O ₂ is at least one oxide selected from the IV elements and is not incorporated in the probeskite lattice) Is disclosed, and a method for producing a dielectric is disclosed, which comprises sintering the compound in the range of 100 to 1200 ° C.

However, the dielectric porcelain obtained by these methods has a large grain size and non-uniformity, and in some cases, it is several tens of degrees.
The characteristics are unstable because of the generation of large particles of up to μ, which is practically unusable especially for laminated capacitors.

On the other hand, in JP-A-54-53300, CuO.MeO _x (where MeO _x is I in the periodic table
At least one oxide of group II, V, VI, VII,
Disclosed is a method for producing a dielectric ceramic, which comprises adding an oxide forming a eutectic mixture (not incorporated into a probeskite lattice) and sintering the mixture in the range of 1000 to 1250 ° C. By this method, a sintered body having a relatively small grain and a uniform size can be obtained, but in practical use, it has drawbacks such as large dielectric loss and low insulation resistance, and the dielectric constant is as low as about 1700 to 3200.

Thallium, which exhibits the best characteristics, is highly toxic and expensive, which poses a serious problem in practical use.

(Problems to be solved by the invention) Therefore, according to the prior art, it is possible to sinter at a temperature of 1200 ° C. or less, a high dielectric constant, a high insulation resistance, a small dielectric loss, a fine grain and a uniform dielectric. Body porcelain compositions are not known.

(Means for Solving the Problems) As a result of various studies, the present inventors have eliminated the above-mentioned drawbacks by combining barium titanate with a specific amount of copper oxide and zinc oxide and / or cadmium oxide. The inventors have found that a dielectric material can be obtained and arrived at the present invention.

That is, the present invention is 87.5-99.6 mol% as the first component
A barium titanate, a second component of 0.2 to 5.5 mol% zinc oxide and / or cadmium oxide, a third component of 0.2 to 7.0 mol% copper oxide, and a dielectric ceramic composition of 87.5 as a first component. ~ 99.6 mol% barium titanate, 0.2-5.5 mol% zinc oxide and / or cadmium oxide as second component, 0.2-7.0 as third component
The present invention relates to a method for producing a dielectric porcelain composition by sintering a mixture of copper oxide having a mol of 5 at a temperature of 1000 to 1200 ° C.

Specific amount of copper oxide and zinc oxide in barium titanate and /
Or a mixture combining cadmium oxide, 1000 ~
Compared to the case of copper oxide alone, sintering at 1200 ℃
The value of tan δ is small, the grain size is small and uniform, and a dielectric ceramic composition having a large insulation resistance can be obtained.
If the sintering temperature is less than 1000 ° C, it will be difficult to obtain dense porcelain.
If the temperature exceeds 00 ° C., grain growth tends to occur, the grain size tends to increase, and the tan δ value tends to increase. Further, zinc oxide is superior to cadmium oxide in exhibiting these characteristics.

Furthermore, by combining at least one specific amount selected from specific titanates, zirconates, and stannates as the fourth component, it is possible to obtain a dielectric constant value near room temperature of 10,000 without impairing the above characteristics. It is possible to change to the above, and it is possible to further reduce the grain size.

The barium titanate used in the present invention may be produced by any method such as a solid phase method, a liquid phase method, an oxalate method and an alkoxide method. When the average particle size is as small as 1 μm or less and the one with a uniform particle size distribution is used, a more uniform fine structure porcelain is obtained, the insulation resistance value becomes large, and the variations in various characteristics become small. .

In the present invention, oxides can be used as they are as zinc oxide, cadmium oxide, and copper oxide, but inorganic salts such as hydroxides and carbonates, oxalates, organic salts such as alkoxides, and any of them can be sintered. Any substance can be used as long as it decomposes to form an oxide below the temperature. As the copper oxide, any one of monovalent, divalent, and coexisting monovalent and divalent can be used.

Further, in the present invention, lead titanate, strontium titanate, barium zirconate, calcium zirconate, strontium zirconate, lead stannate, calcium stannate,
Strontium stannate and barium stannate are PbTi
_{O 3, SrTiO 3, BaZrO 3} , CaZrO 3, SrZrO 3, PbSnO 3, CaSn
The usual complex oxide form of O ₃ , SrSnO ₃ , and BaSnO ₃ is preferably used.

Next, the reason for defining the amount of the additive used in the present invention will be described. The ratio of barium titanate, which is the main component, is 8
It is in the range of 7.5 to 99.6 mol%. The ratio is 99.6 mol%
In the above case, low temperature sintering at 1200 ° C. or less becomes difficult, which causes deterioration of dielectric characteristics and insulation resistance. On the other hand, when the content is 87.5 mol% or less, the substrate is remarkably deformed during sintering, and the dielectric loss is deteriorated, which is not preferable. A more preferable range that has good sinterability, does not cause deformation of the base material, and gives excellent dielectric properties is
It is 92.5-99.4 mol%.

The proportions of zinc oxide and / or cadmium oxide are respectively
The total content of ZnO and CdO is in the range of 0.2 to 5.5 mol%. If it exceeds 5.5 mol%, it is difficult to sinter at a low temperature of 1200 ° C. or lower, and the insulation resistance is small. 0.2 mol%
Below the level, almost no effect of addition is recognized. The most preferable range of good sinterability and sufficiently high insulation resistance is
It is in the range of 0.3 to 3.5 mol%.

The proportion of copper oxide is in the range of 0.2 to 7.0 mol% as CuO. When it is more than 7.0 mol%, the deformation of the base material becomes remarkable and the value of dielectric loss becomes large. Also, the grain size of the sintered body is non-uniform and becomes large. When it is less than 0.2 mol%, low temperature sintering becomes difficult. The preferable range is 0, where the grain size of the sintered body is uniform, deformation of the substrate is hardly seen, and the dielectric loss is extremely small.
It is in the range of 3 to 4.0 mol%.

Furthermore, the best results with good insulation resistance and low dielectric loss are obtained when the molar ratio of zinc oxide and / or cadmium oxide to copper oxide is 1: 3 to 3: 1.

When the proportion of copper oxide is more than 3: 1, the low temperature sinterability at 1200 ° C. or lower is improved, but the dielectric loss increases and the insulation resistance decreases, which is not preferable. On the other hand, if it is less than 1: 3, the low temperature sinterability at 1200 ° C or lower is deteriorated and the density of the sintered body is lowered.

Furthermore, in a preferred embodiment, one or more selected from lead titanate, strontium titanate, barium zirconate, calcium zirconate, strontium zirconate, lead stannate, calcium stannate, strontium stannate, and barium stannate. The complex oxide of the first component, the second
2.5 to 40.0 mol, more preferably 5.0 to 25.0 mol, is added to 100 mol of the sum of the components and the third component. If the amount is less than 2.5 mol, the effect of addition is not so remarkable, the grain size is not reduced, and the value of the dielectric constant is not increased too much. When it exceeds 40.0 mol, the value of dielectric constant tends to be small and the value of insulation resistance tends to be small. A particularly high dielectric constant can be obtained in the range of 5.0 to 25.0 mol%. When barium stannate, calcium stannate, or a mixture thereof is used, it is easy to obtain one having a large dielectric constant.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 Barium titanate, zinc oxide, cadmium oxide, and copper oxide were weighed in the proportions shown in Table 1, pure water was added, and the mixture was mixed using a nylon pot and a nylon ball. After drying the mixture, an appropriate amount of polyvinyl alcohol was added as a binder, and after granulation and drying, a pressure of ² t / cm ² was applied to a diameter of 15 mm and a thickness of 0.6 m.
A disk-shaped molded product of m was prepared. Next, five of these were stacked on a zirconia setter and sintered under the sintering conditions shown in Table 1. 100 mmφ silver electrodes were baked on both sides of the obtained disk porcelain and various characteristics were measured. Dielectric constant and dielectric loss (tan
δ) was measured using an LCR meter under the conditions of 1 KHz, 1 V and 20 ° C. The insulation resistance value was measured by applying a voltage of 500 V using a high insulation resistance meter. Further, a scanning electron micrograph of the surface of the porcelain was taken to determine the grain size. Sintered density is
It was determined by dividing the weight of the disc by the volume obtained by measuring with a micrometer. The measurement results are shown in Table 2. Sample No.
1, 4, 6, 7 are outside the scope of the present invention, and sample Nos. 2, 3, 5 are within the scope of the present invention. As is clear from Table 2, in Material Nos. 2, 3 and 5 which are within the scope of the present invention, all are 12
The density of the sintered body at 00 ° C or less is 5.4 g / cm ³ or more, and at the same time, the grain size is 10 μm or less, which is fine. However, ZnO: CuO is 1: 3
In sample No. 5, which exceeds the above, a slight increase in dielectric loss is observed.

On the other hand, sample Nos. 1, 4, 6, which are out of the scope of the present invention,
Regarding No. 7, when copper oxide alone is used (No. 1), the grain size of the sintered body is extremely large and tends to be nonuniform. In addition, if the added amounts of zinc oxide and copper oxide are each 0.2 mol% or less (No.4) 1200 ℃
It is difficult to sinter at a low temperature below, and conversely, when copper oxide is 7 mol% or more, (No.6) substrate fusion occurs, and when zinc oxide is 5.5% mol or more (No.7), sinterability decreases. Insulation resistance deteriorates Example 2 Barium stannate and calcium stannate were used as the fourth component. Various compounds were weighed in the proportions shown in Table 3, disk-shaped molded products were prepared in the same manner as in Example 1, and sintered under the sintering conditions shown in Table 3. The silver electrode was baked in the same manner as in Example 1 and various characteristics were measured. The average grain size was obtained from the scanning electron micrograph of the porcelain surface using the line intercept method. The measurement results are shown in Table 4. sample
Nos. 2 and 4 are outside the scope of the present invention, and samples Nos. 7 and 9 are outside the scope of the preferred embodiment of the present invention in the amount of the fourth component. As is clear from Table 4, by adding barium stannate and calcium stannate, tan δ was small,
It can be seen that the dielectric constant at 20 ° C can be increased to 10,000 or more and the grain size can be reduced while the insulation resistance remains high.

Example 3 The compositions shown in Table 5 were weighed, alcohol was added, and they were mixed with a nylon ball mill. The resulting mixture is dried to 100
The mixture was passed through a mesh sieve, acrylic resin was used as a binder, trichloroethane was used as a solvent, and a paste was prepared using an agate ball mill. Using the obtained paste, a disk having a diameter of 12 mm and a thickness of 0.4 mm was prepared and sintered under the sintering conditions shown in Table 5. A silver electrode having a diameter of 8 mm was baked and the characteristics were measured in the same manner as in Example 2. The results are shown in Table 6. Also in this example, it can be seen that a dielectric having good characteristics was obtained.

In the above examples, barium titanate having a molar ratio of Ba to Ti of about 1 was used, but good characteristics can be obtained even if the molar ratio deviates by about 0.05 mol. Further, when a small amount of aluminum oxide, silicon dioxide or the like is added to the composition of the present invention, it is effective in improving the characteristics.

(Effects of the Invention) From the above, the dielectric ceramic composition of the present invention is
It can be sintered at a low temperature of 00 ° C or less, has a small tan δ, a uniform and small grain size, and a large insulation resistance.
Further, the dielectric constant at around room temperature can be increased by 10,000 or more without impairing these characteristics, and it is extremely effective as a porcelain composition for laminated ceramic chip capacitors, and its industrial value is great.

Claims (11)

[Claims] 1. A first component of 87.5-99.6 mol% barium titanate, a second component of 0.2-5.5 mol% zinc oxide and / or cadmium oxide, and a third component of 0.2-.
A dielectric ceramic composition comprising 7.0 mol% of copper oxide. 2. The first component is 92.5-99.4 mol% and the second component is
The dielectric ceramic composition according to claim 1, wherein 0.3 to 3.5 mol% and the third component are 0.3 to 4.0 mol%. 3. The dielectric ceramic composition according to claim 1 or 2, wherein the molar ratio of the second component to the third component is 1: 3 to 3: 1. 4. The dielectric ceramic composition according to any one of claims 1 to 3, wherein the second component is zinc oxide. 5. A first component of 87.5-99.6 mol% barium titanate, a second component of 0.2-5.5 mol% zinc oxide and / or cadmium oxide, and a third component of 0.2-.
The composition consisting of 7.0 mol% of copper oxide, as the fourth component, lead titanate, strontium titanate, barium zirconate, calcium zirconate, strontium zirconate, lead stannate, calcium stannate, strontium stannate, stannate. The first component is one or more selected from barium,
A dielectric porcelain composition containing 2.5 to 40.0 mol per 100 mol of the sum of the second component and the third component. 6. The dielectric ceramic composition according to claim 5, wherein the fourth component is 5.0 to 25.0 mol. 7. The dielectric ceramic composition according to claim 5 or 6, wherein the fourth component is barium stannate and / or calcium stannate. 8. A barium titanate of 87.5 to 99.6 mol% as a first component, a zinc oxide and / or cadmium oxide of 0.2 to 5.5 mol% as a second component, and 0.2 to 5.5 as a third component.
87.5-9 as the first component characterized by sintering a mixture consisting of 7.0 mol% copper oxide at a temperature of 1000-1200 ° C
9.6 mol% barium titanate, 0.2-5 as the second component.
A process for producing a dielectric ceramic composition comprising 5 mol% zinc oxide and / or cadmium oxide and 0.2 to 7.0 mol% copper oxide as a third component. 9. The method according to claim 8, wherein the first component of the mixture is 92.5 to 99.4 mol%, the second component is 0.3 to 3.5 mol%, and the third component is 0.3 to 4.0 mol%. 10. The molar ratio of the second component to the third component of the mixture is
The method according to claim 8 or 9, wherein the ratio is 1: 3 to 3: 1. 11. The method according to any one of claims 8 to 10, wherein the second component of the mixture is zinc oxide.