JPH0210791B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a porcelain dielectric composition suitable for use in capacitors based on barium titanate. (Prior Art) Conventionally, in order to obtain dielectric ceramic compositions suitable for capacitor applications from barium titanate and compositions in which shifters, depressors, etc. It was necessary to conclude. (Problems to be Solved by the Invention) However, when sintering at such high temperatures, it causes wear and tear on the expensive setters such as zirconia and the sintering furnace, and a large amount of energy is required for sintering. The resulting product is expensive. Furthermore, in order to manufacture multilayer capacitors using conventional barium titanate-based compositions, it is necessary to use expensive noble metals such as platinum and palladium that can withstand high sintering temperatures as internal electrode materials. However, the resulting multilayer capacitor is extremely expensive. Therefore, wear and tear on the setter and sintering furnace can be reduced, and furthermore, when manufacturing a multilayer capacitor, an inexpensive internal electrode mainly composed of silver can be used. A dielectric ceramic composition that can be sintered at low temperatures is strongly desired. (Means for Solving the Problems) As a result of various studies, the present inventors have found that by combining barium titanate with a specific amount of zinc oxide and/or cadmium oxide and copper fluoride, the above drawbacks can be solved. The present invention was achieved by discovering that it is possible to obtain a dielectric material that does not have a dielectric material. That is, the present invention uses 89.0 to 89.0 as the first component.
99.6 mol% barium titanate as second component
A porcelain dielectric composition comprising 0.2 to 5.5 mol% of zinc oxide and/or cadmium oxide and 0.2 to 5.5 mol% of copper fluoride as a third component. Barium titanate with a specific amount of zinc oxide and/or
Alternatively, a composition combining cadmium oxide and copper fluoride can be sintered at low temperatures below 1200°C, and the resulting porcelain dielectric is made of copper fluoride and copper fluoride.
Compared to when each component is added alone, the value of tanδ is smaller, the grain size is smaller and more uniform,
It has a high insulation resistance value, making it ideal for capacitor applications, especially multilayer ceramic capacitors. Zinc oxide is more effective than cadmium oxide in expressing these properties. Furthermore, by combining a specific amount of one or more selected from specific titanate, zirconate, and stannate as the fourth component, the dielectric constant value near room temperature can be increased to 8000 without impairing the above characteristics. It is possible to make the grain size change even more than that, and it is also possible to make the grain size smaller. 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, or an alkoxide method. The average particle size is
When using particles as small as 1μ or less and with a uniform particle size distribution, a porcelain with a more uniform microstructure can be obtained, the insulation resistance value will be large, and the variations in various properties will be small. In the present invention, CuF ₂ or CuF ₂ .2H ₂ O, which is a hydrated salt, is used as copper fluoride. In the present invention, oxides can be used as they are as zinc oxide and/or cadmium oxide, but inorganic acid salts such as hydroxides, carbonates, and nitrates, and organic salts such as oxalates and alkoxides, all of which are Any material that decomposes to form an oxide below the freezing temperature can be used. In addition, in the present invention, lead titanate, strontium titanate, barium zirconate, calcium zirconate, strontium zirconate, lead stannate, calcium stannate, strontium stannate,
Barium stannate is PbTiO ₃ , SrTiO ₃ ,
_BaZrO3 , _CaZrO3 , _SrZrO3 , _PbSnO3 , _CaSnO3 ,
SrSnO ₃ and BaSnO ₃ in the form of normal composite oxides are preferably used, but when using various precursors, such as copper titanate, an equimolar mixture of lead oxide and titanium oxide may also be used. It is possible. The proportion of barium titanate in the porcelain composition of the invention ranges from 89.0 to 99.6 mol% as _BaTiO3 . If the proportion is more than 99.6 mol%, 1200℃
Sintering becomes difficult at a temperature below 89.0 mol %, and deformation and fusion of the base material occur, which is undesirable. The preferred range is a temperature of 1200℃ or below that provides good sinterability and hardly causes any deformation of the substrate.
It is 92.0 to 99.4 mol%. The proportion of the second component zinc oxide and/or cadmium oxide in the form of ZnO and CdO, respectively, ranges from 0.2 to 5.5 mol% in total. If it exceeds 5.5 mol%, sintering is difficult at low temperatures below 1200°C, and the insulation resistance value is also low. At less than 0.2 mol%,
Almost no effect of addition was observed. The most preferable range for providing good sinterability and sufficiently high insulation resistance is 0.3 to 4.0 mol%. The proportion of copper fluoride, which is the third component, is in the range of 0.2 to 5.5 mol%. If it is more than 5.5 mol%,
Deformation and fusion of the base material becomes more likely to occur, and the value of dielectric loss increases. Also, the sinterable grain size is non-uniform and large. If it is less than 0.2 mol%, low temperature sintering becomes difficult. A preferable range in which the grain sands of the sintered body are small and uniform, almost no deformation of the substrate is observed, and the dielectric loss is small is in the range of 0.3 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 fluoride is 1:3 to 3:1.
It is obtained when 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 composite oxide contains the first component, the second component, and the third component.
It is added in an amount of 2.5 to 40.0 mol, more preferably 5.0 to 25.0 mol, per 100 mol of the total components. The amount is 2.5
Below molar, the effect of addition is less pronounced;
The grain size does not decrease, and furthermore, the dielectric constant value does not increase significantly. When the amount exceeds 40.0 mol, the dielectric constant value tends to be small and the insulation resistance value tends to be small. Particular dielectric constants are obtained in the range of 5.0 to 25.0 mol%. When barium stannate, calcium stannate, or a mixture thereof is used, a material with a large dielectric constant can be easily obtained. (Examples) Hereinafter, the present invention will be explained in detail by way of examples. Example 1 Barium titanate, copper fluoride, zinc oxide and/or cadmium oxide were weighed in the proportions shown in Table 1, and mixed in an agate ball mill using vinyl acetate as a binder and acetone as a solvent. After drying the mixture, it was granulated through an 80-mesh sieve and granulated with a pressure of 2t/ ^cm2 to a diameter of 15mm and a thickness.
A 0.6 mm disc-shaped molded product was created. Next, 10 of these were stacked on a zirconia setter and sintered under the sintering conditions shown in Table 1. Silver electrodes with a diameter of 10 mm were baked on both sides of the resulting porcelain disc, and various properties were measured. The dielectric constant and dielectric loss (tan δ) were measured using an LCR meter at 1 KHz, 1 V, and 20°C. The insulation resistance value was measured using a high insulation resistance meter and applying a voltage of 500V. In addition, a scanning electron micrograph of the porcelain surface was taken to determine the grain size. The sintered density was determined by dividing the weight of the disc by the volume measured using a micrometer. The measurement results are shown in Table 2. Samples Nos. 1, 2, and 3 are outside the scope of the present invention. As is clear from Table 2, those within the scope of the present invention can be sintered at 1200° C. or lower, have high insulation resistance, high sintered body density, and small grain size.

【table】

[Table] Example 2 The results of the system in which the fourth component was added are shown. Various compounds were weighed in the proportions shown in Table 3, ethyl alcohol was added, and ball milling was performed using a nylon ball to mix thoroughly. After drying the resulting mixture,
A paste was prepared using an acrylic resin as a binder and trichloroethane as a solvent using a Meno ball mill. A green sheet with a thickness of 30 μm was prepared by the doctor blade method. 25 of these green sheets were stacked together and laminated at a temperature and pressure of 70° C. and 100 kg/cm ² , and then cut into squares with an opening of 12 mm. After sintering under the conditions shown in Table 4, silver electrodes were baked on both sides, and various properties were measured in the same manner as in Example 1. The average grain size was determined from the scanning electron micrograph of the porcelain surface using the line intercept method. The measurement results are shown in Table 4. Samples Nos. 1, 2, and 9 are outside the scope of the present invention, and Samples Nos. 7 and 8 have amounts of the fourth component that are outside the scope of the preferred embodiment of the present invention.
As is clear from Table 4, by adding the fourth component, tan δ remains small and insulation resistance remains high.
It can be seen that the dielectric constant at 20°C can be increased to over 8000, and the grain size can also be reduced. In addition, the amount of the fourth component is shown as an internal division.

【table】

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

【table】

[Table] In the above examples, barium titanate is
The molar ratio of Ba and Ti was approximately 1, but
Even if the ratio deviates by about 0.05 mole, good characteristics can be obtained. Further, when a trace amount of aluminum oxide, silicon dioxide, etc. 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 ceramic composition of the present invention can be sintered at a low temperature of 1200° C. or lower, has a small tan δ, a uniform and small grain size, and has a large insulation resistance. In addition, the dielectric constant at room temperature can be increased to over 8000 without impairing these properties, making it extremely effective as a ceramic composition for laminated ceramic chip capacitors, and its industrial value is great.

Claims (1)

[Claims] 1 89.0 to 99.6 mol% barium titanate as the first component, 0.2 to 5.5 mol% zinc oxide and/or cadmium oxide as the second component, and 0.2 to 5.5 mol% futon as the third component. A porcelain dielectric composition consisting of copper chloride. 2 The first component is 92.0 to 99.4 mol%, the second component is 0.3
4.0 mol% and the third component is 0.3 to 4.0 mol%. 3 The molar ratio of the second component and the third component is 1:3 to 3:
1. The porcelain dielectric composition according to claim 1 or 2, which is 4. The porcelain dielectric composition according to any one of claims 1 to 3, wherein the second component is zinc oxide. 5 A composition consisting of 89.0 to 99.6 mol% barium titanate as the first component, 0.2 to 5.5 mol% zinc oxide and/or cadmium oxide as the second component, and 0.2 to 5.5 mol% copper fluoride as the third component. As the fourth component, lead titanate, strontium titanate, barium zirconate, calcium zirconate, strontium zirconate, lead stannate,
One or more selected from calcium stannate, strontium stannate, and barium stannate in an amount of 2.5 to 40.0 per 100 moles of the sum of the first component, second component, and third component.
A porcelain dielectric composition containing mol. 6. The ceramic dielectric composition according to claim 5, wherein the fourth component is 5.0 to 25.0 moles. 7. The porcelain dielectric composition according to claim 5 or 6, wherein the fourth component is barium stannate and/or calcium stannate.