JPH0238540B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a dielectric ceramic composition based on barium titanate that can be sintered at low temperatures. (Prior technology) Porcelain made by sintering perovskite oxide, typically barium titanate, is used in capacitors, PTC
It is used for various purposes such as elements and piezoelectric elements. Generally, in order to sinter barium titanate, mixed crystals of barium titanate and other perovskite oxides, and mixtures of barium titanate and other perovskite oxides densely enough for practical use, it is necessary to Temperatures above 1,350 to 1,400 degrees Celsius were required. However, when sintering at such high temperatures, it causes wear and tear on the setters and sintering furnaces made of expensive zirconia and alumina, and a large amount of energy is required for sintering, making the resulting products expensive. Become something. In addition, for example, in order to manufacture a multilayer capacitor using a conventional barium titanate-based composition, as an internal electrode material,
It is necessary to use expensive noble metals such as platinum and palladium that can withstand high sintering temperatures, and the resulting multilayer capacitors are significantly expensive. Therefore, wear and tear on the setter and sintering furnace can be reduced, and furthermore, when manufacturing multilayer capacitors,
There is a strong desire for a dielectric ceramic composition that can be sintered at low temperatures and allows the use of inexpensive silver-based internal electrodes. In JP-A-58-135178, barium titanate 100
By adding 3.9 to 21.6 moles of lithium oxide to the mole, 3.4 to 20.4 moles of fluoride was added to 100 moles of barium titanate for the purpose of imparting low-temperature sinterability and improving the electrical properties of the resulting porcelain. A mixture containing zinc (ZnF ₂ ) is sintered at a temperature of 930°C,
A technique for manufacturing a laminated ceramic capacitor is disclosed. (Problem to be solved by the invention) However, when lithium, which is a monovalent metal,
When added in large amounts (mole), there is a drawback that durability performance such as high temperature load characteristics and moisture resistance characteristics are likely to deteriorate. Furthermore, if large amounts of lithium oxide and zinc fluoride are present, the amount of components that will volatilize during sintering will increase, so when a mixture containing large amounts of these is sintered, deformation of the base material is likely to occur, and industrial The disadvantage is that it is difficult to obtain a product in a stable manner. Furthermore, when lithium oxide and zinc fluoride are present in such large amounts, grain growth tends to occur during sintering, and the insulation resistance and mechanical strength of the porcelain tend to decrease. (Means for Solving the Problems) As a result of various studies, the present inventors found that by combining barium titanate and a small amount of zinc fluoride, the temperature of 1200°C or less, which is suitable for the combination of
Can be sintered at temperatures below 1150℃, for example, silver can be sintered at temperatures below 80℃.
The present invention was achieved by discovering that a multilayer capacitor can be made using a silver-palladium electrode containing 70% by weight. That is, in the present invention, as the first component, 97.0 to
99.7 mol% barium titanate as second component
It is a dielectric ceramic composition consisting of 0.3 to 3.0 mol% of zinc fluoride, and the present invention also comprises 60.0 to 97.5 mol% of barium titanate as the first component and 0.3 to 3.0 mol% of barium titanate as the second component. Zinc fluoride, 2.2 to 37.0 mol% calcium titanate as the third component,
A dielectric comprising one or more selected from strontium titanate, lead titanate, calcium zirconate, strontium zirconate, barium zirconate, lead zirconate, calcium stannate, strontium stannate, barium stannate, and lead stannate. The present invention is a ceramic composition, and the present invention further provides 0.05 to 1.0 parts by weight of silicon dioxide to 100 parts by weight of the composition consisting of 97.0 to 99.7 mol% of the first component and 0.3 to 3.0 mol% of the second component. This is a dielectric ceramic composition containing. In the present invention, barium titanate is used as the first component, and calcium titanate, strontium titanate, lead titanate,
Calcium zirconate, strontium zirconate, barium zirconate, lead zirconate, calcium stannate, strontium stannate, barium stannate, and lead stannate (hereinafter referred to as perovskite oxide as the third component) are used. In addition, as the second component zinc fluoride, _{ZnF 2} or ZnF 2.4H ₂ O
hydrated salt is used. In the present invention, zinc fluoride and one or more selected from barium titanate or barium titanate and a perovskite oxide as a third component,
A dielectric composition is obtained by sufficiently uniformly mixing using a ball mill or the like, and molding and sintering by a known method. Various forms of barium titanate and perovskite oxide as the third component are used when mixed with zinc fluoride. For example, a compound having the chemical formula BaTiO ₃ is used as barium titanate, or a mixture of equimolar amounts of titanium oxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) is mixed with ZnF ₂ . In the latter case, the material is pre-calcined at a temperature of about 900 to 1100°C, pulverized and classified, then shaped and sintered. For example, when obtaining a sintered body made of barium titanate and barium stannate,
Even if ZnF ₂ is added to a mixture of BaTiOC ₃ and BaSnO ₃ , a solid solution of Ba(TiSn)O ₃ is made in advance and then added to it.
ZnF ₂ may also be added. The more homogeneous the mixing state of barium titanate or barium titanate and the third component perovskite oxide and zinc fluoride, the better. For this purpose, use a fine powder as the starting material and thoroughly mix it with a ball mill or the like. Mixing is preferred. Also,
Since zinc fluoride has a solubility in water of 1 to 2 g, it can also be dissolved in water and mixed with barium titanate or barium titanate and the perovskite oxide as the third component. Furthermore, the particle size of the powder to be subjected to sintering is preferably as fine as possible, preferably 0.07 to 1μ, more preferably
A thickness of 0.07 to 0.5μ is desirable. When the zinc fluoride contained in the dielectric ceramic composition of the present invention is 0.3 to 3.0 mol%, the sinterability is good;
It is most preferable because the density is easy to increase and no deformation of the element body is observed. When obtaining a capacitor with a high dielectric constant, the first
The component is 60.0 to 97.5 mol%, and the second component is 0.3 to 3.0
Preferably, the third component is 2.2 to 37.0 mol%. Furthermore, the first component is 80.0 to 95.0 mol%
The second component is 0.3 to 3.0 mol%, and the third component is 4.7 to 3.0 mol%.
The one with 17.0 mol% shows the highest dielectric constant. The composition of the present invention has a first component of 97.0 to 99.7 mol%.
and a mixture consisting of 0.3 to 3.0 mol% of the second component,
Or first component 60.0 to 97.5 mol%, second component 0.3
It is obtained by sintering a mixture consisting of ~3.0 mol% and a third component of 2.2-37.0 mol% at a temperature of 1000-1200°C. If the temperature is lower than 1000°C, hardly any sintering will occur, and if it is higher than 1200°C, significant grain growth will occur, which is not preferable. A temperature range of 1,000 to 1,150°C is preferable because the resulting porcelain grains are uniform, the density is easy to increase, and no deformation is observed. By adding 0.05 to 1.0 parts by weight of silicon dioxide to 100 parts by weight of barium titanate or a mixture of barium titanate and the third component, perovskite oxide and zinc fluoride, the sinterability of the substrate is stabilized. Insulation resistance and mechanical strength are also improved. If the proportion is less than 0.05 parts by weight, no effect of addition will be observed;
If it exceeds 1.0 parts by weight, sinterability deteriorates and the dielectric constant decreases. Various types of silicon dioxide can be used. If fine powder is uniformly dispersed, good results are likely to be obtained. Aerosil is suitable for this purpose.
Suitable sources include SiO ₂ , colloidal SiO ₂ dispersed in water, and liquid SiO ₂ sources such as ethyl silicate. (Examples) Hereinafter, the present invention will be explained in detail by way of examples. Example 1 Barium titanate and zinc fluoride were weighed in the proportions shown in Table 1, ethyl alcohol was added, and they were thoroughly mixed using a nylon ball mill. After drying the mixture, an appropriate amount of polyvinyl alcohol was added as a binder, and after granulation and drying, a disk-shaped molded product with a diameter of 15 mm and a thickness of 0.6 mm was created under a pressure of 2 t/cm ² . Next, five sheets of this were stacked on a zirconia setter and sintered at a maximum temperature of 1075 to 1150°C. The density of the sintered body was determined by the volume calculated from the thickness and diameter of the disc, which were measured using a micrometer. The results are shown in Table 1. Sample No. 1 is a case in which ZnF ₂ is not added, and the density of the sintered body when held at the maximum temperature of 1150° C. for 3 hours is as low as 4.5 g/cm ³ . In sample No. 2
ZnF ₂ was added at 1.5 mol %, and in No. 3, 3.0 mol %.
Each sintered body had a density of 5.6 g/cm ³ and was almost completely sintered. In the case of No. 3, slight deformation was observed in three of the five porcelain pieces, the top two and the bottom one. Sample No. 4 is obtained by adding 0.1% by weight of Aerosil SiO ₂ to No. 3. In this case, no deformation was observed in the porcelain. In addition, the density of the sintered body was also slightly improved.
When 7.0 mol% of ZnF ₂ was added (No. 5), fusion and deformation of the substrates occurred, and the density of the sintered body could not be calculated.

[Table] Example 2 Barium titanate, barium stannate, calcium stannate, barium zirconate, lead titanate and zinc fluoride were combined. Various compounds were weighed in the proportions shown in Table 2, pure water was added, and the mixture was sufficiently mixed in a nylon ball mill, followed by drying. A paste was prepared using a ball mill using an acrylic resin as a binder and trichloroethane as a solvent. A green sheet with a thickness of 50 μm was prepared by the doctor blade method. Ten of these green sheets were stacked and laminated at 70° C. and a pressure of 70 kg/cm ² , and then cut into squares with an opening of 15 mm. After sintering this material under the firing conditions shown in Table 2, a silver electrode with a diameter of 8 mm was baked on it and various electrical properties were measured. Measure the dielectric constant and dielectric loss (tanδ) using an LCR meter.
Measured under the conditions of 1KHz, 1V, and 20℃. The insulation resistance value was measured using a high insulation meter and applying a voltage of 500V. The average grain size was determined from a scanning electron micrograph of the porcelain surface using the line intercept method. The results are shown in Table 3. Sample No. 1 was a case in which ZnF ₂ was not added, and sintering did not proceed. Sample No.
2, 3, and 4 are those with ZnF ₂ and SiO ₂ added,
It can be seen that sintering progressed almost completely and the electrical properties were good. Sample No. 5 was obtained without adding SiO ₂ , and out of the 20 sintered samples, 5 had some warpage. Grain growth occurred at a sintering temperature of 1225°C (No. 6). Grain growth also occurred when lithium oxide was present (No. 7).

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【table】

[Table] In the above examples, barium titanate and perovskite oxide as the third component were used in which the molar ratio of element A to element B was approximately 1, but it is acceptable even if the ratio deviates by about 0.05 mole. characteristics can be obtained. (However, the perovskite oxide is expressed by the general formula ABO _3. ) Furthermore, when a small amount of aluminum oxide is added to the composition of the present invention, it is effective in improving the characteristics. (Effects of the Invention) As described above, the dielectric composition of the present invention has
It can be sintered at a low temperature of 1000-1200℃, keeping the grain size small and reducing the dielectric constant near room temperature.
It can be increased to over 6000. For example, when this dielectric composition is used for multilayer ceramic capacitors, it is possible to use inexpensive internal electrodes made of silver/palladium containing about 70 to 80% silver, and it is also possible to Its industrial value is extremely high, as there is little wear and tear and porcelain can be produced stably.

Claims (1)

[Scope of Claims] 1. A dielectric ceramic composition comprising 97.0 to 99.7 mol% of barium titanate as a first component and 0.3 to 3.0 mol% of zinc fluoride as a second component. 2 60.0-97.5 mol% barium titanate as the first component, 0.3-3.0 mol% zinc fluoride as the second component, 2.2-37.0 mol% calcium titanate, strontium titanate, lead titanate as the third component , calcium zirconate, strontium zirconate, barium zirconate, lead zirconate, calcium stannate, strontium stannate,
A dielectric ceramic composition comprising one or more selected from barium stannate and lead stannate. 3 80.0-95.0 mol% barium titanate as the first component, 0.3-3.0 mol% zinc fluoride as the second component, 4.7-17.0 mol% calcium titanate, strontium titanate, lead titanate as the third component , calcium zirconate, strontium zirconate, barium zirconate, lead zirconate, calcium stannate, strontium stannate,
The dielectric ceramic composition according to claim 2, comprising one or more selected from barium stannate and lead stannate. 4 0.05 to 1.0 parts by weight of silicon dioxide is contained per 100 parts by weight of a composition consisting of 97.0 to 99.7 mol% barium titanate as the first component and 0.3 to 3.0 mol% zinc fluoride as the second component. A dielectric porcelain composition made of