JPH0522372B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a composition for a grain-boundary insulated semiconductor ceramic capacitor. Conventionally, small-sized, large-capacity capacitors include barrier layer capacitance type semiconductor ceramic capacitors, surface insulation layer type semiconductor ceramic capacitors, and grain boundary insulation type semiconductor ceramic capacitors. Among these, weir layer capacitance type semiconductor ceramic capacitors are
Although it shows a capacitance value of 400 to 500 nF/cm ² , tan δ is as large as 4 to 5%, and the insulation resistance (IR) is only 1 MΩ. Furthermore, surface insulating layer type semiconductor ceramic capacitors do not have good characteristics such as tan δ, capacitance temperature characteristics, capacitance change rate, and distortion rate. Furthermore, grain boundary insulated semiconductor ceramic capacitors exhibit superior electrical properties in most respects compared to surface insulated layer type semiconductor ceramic capacitors, but their capacitance is at most 300 nF/cm ² . Therefore, this invention has a capacitance of 400~
The purpose of the present invention is to obtain a ceramic composition capable of producing a grain boundary insulated semiconductor ceramic capacitor exhibiting a large value of 500 nF/cm ² . Another object of the present invention is to provide a grain-boundary insulated semiconductor ceramic composition that exhibits stable characteristics even when the composition ratio varies. In other words, the gist of this invention is:
(Ba _1-x Sr _x ) (Ti _1-y Zr _y ) O ₃ (0.9≦2x＋3y≦2.3,
0.4≧x, 0.6≧y) or (Ba _1-x Sr _x ) (Ti _1-y
Zr _y ) O ₃ (0.9≦2x＋3y≦2.3, 0.4≧x, 0.6≧y)
The main components include titanate and zirconate, as well as rare earth elements such as La and Y,
Semiconductor porcelain containing a semiconducting agent such as Nb, Ta, W, etc. and having a maximum crystal grain size of 100 to 250 μm, the crystal grain boundaries of the semiconductor porcelain being made into an insulator by a metal oxide. It is a field insulated semiconductor ceramic composition. Among the above, in (Ba _1-x Sr _x ) (Ti _1-y Zr _y ) O ₃ , x and y are 0.9≦2x+3y≦2.3, 0.4≧x, 0.6
It is necessary to have a relationship of ≧y in order to obtain good characteristics. This is because when 2x+3y becomes less than 0.9, the capacitance decreases, while when 2x+3y exceeds 2.3, the capacitance decreases. Moreover, when x exceeds 0.4, it becomes difficult to obtain crystal grains with a large grain size. Furthermore, if y exceeds 0.6, the capacitance decreases. FIG. 1 shows the quantitative correlation between x and y, and the area surrounded by polygons indicates the area within the scope of the invention. In addition, (Ba _1-x Sr _x ) (Ti _1-y Sr _y )O ₃ can be combined with other titanates such as CaTiO ₃ , CaZrO ₃
When at least one kind of zirconate such as is contained, the amount to be contained is suitably 10 mol% or less. This is because if the content exceeds 10 mol%, the effects of its inclusion, such as improvement in sinterability and reproducibility of electrical properties, cannot be expected. Furthermore, the content range of the semiconducting agent is 0.1
~1.0 mol% is preferred. Outside this range, even if fired in a neutral or reducing atmosphere, the
Semiconductor porcelain having a value of about 10 ^-1 Ω·cm cannot be obtained. Furthermore, semiconductor porcelain contains SiO ₂ , Al ₂ O ₃ ,
Although it is permissible to include at least one type of TiO ₂ , the effect of its inclusion is that the firing temperature can be lowered and dielectric breakdown can also be increased. Among these, the content range of SiO ₂ is 0.05~
0.5 mol% is preferred. This is 0.05 mol% _SiO2
If it is less than 0.5 mol %, the firing temperature will still be high and the effect of its addition will not be apparent, and if it exceeds 0.5 mol %, a decrease in the dielectric constant will be observed. Moreover, the content range of Al ₂ O ₃ is preferably 0.02 to 0.2 mol %. This means that if it is less than 0.02 mol%, the effect of increasing dielectric breakdown cannot be obtained.
If it exceeds 0.2 mol%, a decrease in dielectric constant is observed. Further, the content range of TiO ₂ is preferably 0.05 mol% or less. This is because if the content exceeds 0.05 mol %, it is difficult to obtain crystals with a large particle size and sufficient capacitance cannot be obtained. For example, metals such as Pb, Bi, Cu, B, Mu,
There are compounds such as oxides, and a method of diffusing them at grain boundaries by heat treatment is adopted. Other methods of insulating grain boundaries include applying it to the surface of semiconductor porcelain by dry plating such as vapor deposition or sputtering, and then heat-treating it, or applying a compound paste and heat-treating it. This semiconductor porcelain composition is produced by mixing raw materials in a predetermined ratio, molding them into a certain shape, and then firing them in a neutral or reducing atmosphere. A diameter in the range of 100 to 250 μm brings about favorable electrical properties. If the maximum grain size is less than 100 μm,
The capacitance, capacitance temperature characteristics, and capacitance change rate will decrease. Moreover, if the thickness exceeds 250 μm, the electrical characteristics deteriorate and it becomes an obstacle to thinning the film to obtain a large capacitance. In addition, by incorporating Mn in the range of 0.02 to 0.5 mol% into semiconductor porcelain, insulation resistance (IR) can be improved.
can be improved. Semiconductor porcelain is allowed to contain unavoidable impurities to the extent that it does not adversely affect its properties, but for example, if it contains ZnO, Bi ₂ O ₃ , CuO, etc., it may affect sinterability and reproducibility. etc. has an effect. Although the range in which it is contained cannot be clearly defined, it may be contained in a small amount in order to improve properties. Hereinafter, this invention will be explained in detail according to examples. Example BaCO ₃ , SrCO ₃ , TiO ₂ , CaTiO ₃ , BaZrO ₃ was used to obtain semiconductor porcelain having the composition ratio shown in Table 1.
Main materials such as Y ₂ O ₃ , La ₂ O ₅ , WO ₃ , Nb ₂ O ₅ ,
Semiconducting agents such as Er ₂ O ₃ and mineralizing agents such as SiO ₂ , Al ₂ O ₃ and TiO ₂ were weighed and mixed, and calcined at 1100° C. for 2 hours. Next, 10% by weight of vinyl acetate resin was added, wet-pulverized, sieved through a 30-mesh sieve, and then molded into a disc with a diameter of 10 mmφ and a wall thickness of 0.5 mm at a molding pressure of 750 kg/cm ² . The molded disk was heat treated at 1150°C in a natural atmosphere, and then fired at 1400°C for 2 to 4 hours in a reducing atmosphere consisting of 98% nitrogen and 2% hydrogen by volume.
A semiconductor porcelain was obtained. In order to make the grain boundaries of the obtained semiconductor porcelain an insulator, a metal oxide paste prepared in advance was applied to the surface of the semiconductor porcelain by a coating method, and heat treatment was performed in air at 1150°C for 2 hours to transform the grain boundaries. Made into an insulator. The following types of metal oxide pastes were used, and the metal oxide pastes applied to each sample are shown in Table 1 with symbols A, B, and C. A: Pb ₃ O ₄ 40% by weight, Bi ₂ O ₃ 10% by weight, resin varnish 50% by weight B: Bi ₂ O ₃ 42% by weight, CuO 4% by weight, MnCO ₃
4% by weight, resin varnish 50% by weight C: Pb ₃ O ₄ 45% by weight, H ₂ BO ₂ 5% by weight, resin varnish 50% by weight Furthermore, silver paste was printed and applied on both sides of the grain boundary insulated semiconductor porcelain. , the capacitor was created by baking at 800℃ for 30 minutes. The electrical characteristics of the obtained capacitor were measured and the results are shown in Table 2. Items marked with * in Tables 1 and 2 are outside the scope of this invention, and the others are within the scope of the invention.

【table】

【table】

[Table] The electrical properties in Table 1 are values measured under the following conditions. Capacitance (Cs), dielectric loss (tanδ): +20℃,
Values measured at a frequency of 1KHz and a voltage of 0.2Vrms or less. Insulation resistance (IR): Value at +20°C, 30 seconds after applying a DC voltage of 10 V per mm of sample thickness. Capacitance temperature characteristic (△TC): Value indicating the maximum capacitance change rate in the temperature range of -25°C to +85°C, with +20°C as the standard. Capacitance change rate (DCB): Based on the capacitance when a DC voltage of 0.2V is applied at +20℃,
The value expressed as a percentage of the change in capacitance when a DC voltage of 10V is applied. Distortion rate: Value showing the total high frequency distortion rate at +20℃, frequency 1KHz, and applied voltage 1V. Frequency characteristics (ESR): Value around 1MHz. As is clear from the above examples, by constructing a capacitor using the grain boundary insulated semiconductor ceramic composition according to the present invention, Cs, △TC,
Practically sufficient values of tanδ, DCB, distortion rate, and ESR were obtained. Furthermore, while the tolerance for deviations in molar ratio with conventional compositions was about 1/1000, this invention has a tolerance of more than 5/1000, and stable characteristics can be achieved even with deviations in the formulation composition. It has the effect of being

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the correlation between X (Sr amount) and Y (Zr amount).

Claims (1)

[Claims] 1 (Ba _1-x Sr _x ) (Ti _1-y Zr _y ) O ₃ (0.9≦2x＋3y≦
2.3, 0.4≧x, 0.6≧y) or (Ba _1-x Sr _x )
(Ti _1-y Zr _y ) O ₃ (0.9≦2x＋3y≦2.3, 0.4≧x, 0.6
≧y) and other main ingredients including titanate and zirconate, contains rare earth elements such as La and Y, and semiconducting agents such as Nb, Ta, and W, and has a maximum crystal grain size. A grain boundary insulated semiconductor porcelain composition comprising semiconductor porcelain having a diameter of 100 to 250 μm, wherein the grain boundaries of the semiconductor porcelain are made into an insulator with a metal oxide.