JPH0449508B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a high dielectric ceramic composition suitable for use in grain boundary type semiconductor ceramic capacitors. [Prior Art and its Problems] Dielectric ceramic compositions based on barium titanate, strontium titanate, and the like have been well known. However, when these compositions are used as grain boundary semiconductor ceramic capacitors, although barium titanate has a high dielectric constant,
There is a problem that the capacitance temperature change rate is large, and various strontium titanate systems are being considered, but when used in audio equipment, communication equipment, etc., the electrical characteristics are still insufficient, and if the dielectric constant is high, There are problems such as large dielectric loss, poor temperature characteristics, and low insulation resistance.If dielectric loss is small, there are problems such as low preferential conductivity. It has been desired to develop a dielectric constant ceramic composition having balanced electrical properties such as a high dielectric constant and good temperature characteristics. [Means for Solving the Problems] It is an object of the present invention to have a particularly high dielectric constant, good temperature characteristics, and small dielectric loss when used as a grain boundary type semiconductor ceramic capacitor. An object of the present invention is to provide a high dielectric constant ceramic composition having high insulation resistance and well-balanced electrical properties. The present invention provides 5 to 28 mmol of strontium stannate per 1 mole of strontium titanate.
The present invention relates to a high dielectric constant ceramic composition containing 0.5 to 3.5 mmol of a semiconducting agent and 2.5 mmol or less (excluding 0) of manganese dioxide. Each of the above-mentioned components is used so as to have substantially the above-mentioned composition, and within that range the purpose can be achieved, but outside the range, the characteristics of the present invention such as temperature characteristics, dielectric loss, dielectric constant, and insulation resistance may be affected. Balance is impaired. That is, when the amount of strontium stannate is large (more than 28 mmol) per mole of strontium titanate, the dielectric constant decreases, and when the amount is less than 5 mmol, the capacitance temperature change rate increases. Further, when the amount of the semiconductor forming agent exceeds 3.5 mmol, the dielectric constant decreases, and when the amount is less than 0.5 mmol, the dielectric constant and insulation resistance decrease. When the amount of manganese dioxide exceeds 2.5 mmol, the rate of capacitance temperature change increases. The method for producing the high dielectric constant ceramic composition of the present invention does not need to be particularly limited, and the following production method is generally practical. namely strontium titanate,
Strontium stannate, a semiconducting agent, manganese dioxide, and optionally a mineralizing agent are weighed to have a predetermined composition, and the oxides, carbonates, etc. of each component are weighed and wet-mixed using a ball mill or the like. As raw materials for strontium titanate and strontium stannate used in the present invention, each of the above components may be used as is, or Ti,
Oxides of Si and Sn, carbonates that become oxides when heated,
Oxalate can be selected and used as appropriate. Further, the semiconductor agent used in the present invention may be an oxide such as lanthanum oxide, niobium oxide, yttrium oxide, tantalum oxide, or tungsten oxide, or one that becomes an oxide when heated. Further, as a raw material for manganese dioxide used in the present invention, it may be used as it is, or a carbonate or the like which becomes an oxide upon heating may be appropriately selected and used. Furthermore, in the present invention, a small amount of conventionally known mineralizing agents may be used, such as SiO ₂ , Al ₂ O ₃ , ZnO, and the like. When using a mineralizing agent, the temperature characteristics may be impaired if the mineralizing agent is used in an excessively large amount, so the amount used is usually preferably 15 mmol or less per 1 mole of strontium titanate. After wet mixing the above components, 900~1400℃,
It is preferably calcined at 1000 to 1300°C. Furthermore, a binder such as polyvinyl alcohol is added to this calcined product, and after pressure molding, it is fired at 1300 to 1500°C, preferably 1400 to 1450°C, in a neutral or reducing atmosphere to form a high dielectric constant porcelain composition. Obtainable. The high dielectric constant ceramic composition of the present invention is suitably used as a grain boundary type semiconductor ceramic capacitor, and any known method can be adopted as a method for manufacturing the capacitor. That is, CuO, Bi ₂ O ₃ and MnO ₂ are added to the above composition.
A grain boundary type semiconductor ceramic capacitor can be obtained by applying an insulating agent such as, heat-treating in air at 1000 to 1300°C, and then baking the electrodes using silver paste or the like. [Example] Strontium stannate and semiconductor agent as shown in Table 1 per mole of strontium titanate.
Take a predetermined amount of Nb ₂ O ₅ , MnO ₂ , mineralizer, etc.
Wet mixing was performed in a ball mill (each component is shown in mmol in the table). Then, it was dried, crushed, and calcined at 1000-1300 in an air atmosphere. After crushing this calcined product, add and mix an organic binder such as polyvinyl alcohol to make it homogeneous, dry, crush, and bake.
It was pressure molded into a disc or square plate shape at a pressure of 1000 Kg/cm ² . The thus pressure-molded product was fired at 1400 to 1450°C in a nitrogen atmosphere. Next, to this baked product
At least one of CuO, Bi ₂ O ₃ , MnO _{2 ,} etc. was applied, and a diffusion treatment was performed at 1000 to 1300° C. in an air atmosphere. Apply silver paste to this surface and apply 800
Electrodes were formed by baking at °C. Table 2 shows the results of electrical characteristics and temperature characteristics. In the same table, the dielectric constant (denoted as εr) and dielectric loss (denoted as tanδ) are values measured at a temperature of 25° C. and a frequency of 1 KHz. In addition, the capacitance temperature change rate (denoted as TC), which represents temperature characteristics, is -25℃ with 25℃ as the standard.
Evaluation was made based on the change in value between ℃ and +85℃. In addition, the insulation resistance (denoted as IR) is measured at an applied voltage of 50V.
This is the value when the DC voltage is set to .

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[Table] [Effects of the invention] The ceramic composition of the present invention exhibits a high dielectric constant of 60,000 or more, and when used as a grain boundary type semiconductor ceramic capacitor, has a small dielectric loss of 1 to 3.5% and a dielectric constant of 6,500 to 3.5%.
High insulation resistance of 62400MΩ-cm and especially +5.0
Because it has good temperature characteristics of ~-4.9%,
For example, it can exhibit well-balanced electrical characteristics for grain boundary type semiconductor ceramic capacitors in audio equipment and communication equipment.

Claims (1)

[Claims] 1. For 1 mole of strontium titanate, 5 to 28 mmol of strontium stannate, 0.5 to 3.5 mmol of a semiconducting agent, and 2.5 mmol of manganese dioxide.
A high dielectric constant ceramic composition characterized by containing a millimol or less (excluding 0).