CN1142476A - Semiconductor ceramics and manufacturing method thereof - Google Patents

Abstract

The present invention provides a semiconductor ceramic that is less likely to break even when a high voltage is applied and has excellent destructive properties against rush current, and a method for manufacturing the same. The steps of the method are: weighing BaCO ₃ , SrCO ₃ , Pb ₃ O ₄ , CaCO ₃ , TiO ₂ , Er ₂ O ₃ , MnCO ₃ and SiO ₂ to form (Ba _0.0536 Pb _0.08 Sr _0.20 Ca _0.18 Er _0.04 ) composition of TiO ₃ +0.0004Mn+0.02SiO ₂ . Mixed and dehydrated. After drying, it was calcined at 1360°C for 2 hours. After mixing the obtained calcined powder with a binder, it was made into a formed body with a diameter of 18mm and a thickness of 3.6mm, and fired at 1360°C for 1 hour. Cool down to obtain semiconductor porcelain.

Description

Semiconductor porcelain and its manufacturing method

The invention relates to barium titanate series semiconductor ceramics and a manufacturing method thereof.

Barium titanate series semiconductor ceramics (hereinafter referred to as semiconductor ceramics) with positive resistance temperature characteristics are widely used in electric motors because of their sharp increase in resistance at temperatures above the Curie point. Starter, color TV picture tube and other uses.

However, when the surge current generated by applying a voltage to the semiconductor ceramic reaches a value higher than that which destroys its characteristics (hereinafter referred to as the impulse withstand voltage characteristic), layer damage occurs.

The reason for this phenomenon, on the one hand, is that the outer part of the semiconductor ceramics contacts the outside air to accelerate the heat diffusion, so that the temperature of this part is low, and the resistance is also lower; on the other hand, the inner part of the semiconductor ceramics and the outer part Part of it is slower than its thermal diffusion, so that the resistance increases, so that the heating of the semiconductor ceramic is uneven.

As a method of manufacturing semiconductor ceramics that does not cause such ceramic damage, as described in JP-A-4-154661, a method of firing semiconductor ceramics in air, followed by reduction treatment, and then reoxidation treatment in the atmosphere has been proposed. .

However, in the method of reducing and then oxidizing semiconductor ceramics, if the reoxidation treatment is insufficient, the withstand voltage is low, and when the oxidation treatment is aggravated, its resistivity increases at room temperature.

The object of the present invention is to provide a semiconducting porcelain which is excellent in impulse withstand voltage characteristics and hardly breaks the porcelain, and a method for producing the same.

In the present invention according to claim 1, in barium titanate series semiconductor ceramics having positive resistance temperature characteristics, the resistance value between the surface part and the center part of the semiconductor ceramics is higher than that of the surface part or the center part of the semiconductor ceramics. resistance.

In the semiconductor porcelain of the present invention as claimed in claim 2, the resistance value between the surface part and the center part is 15-68% higher than the resistance value of the surface part or the center part.

The barium titanate series semiconductor porcelain of the present invention according to claim 3 contains lead oxide, strontium oxide and calcium oxide.

The manufacturing method of the semiconductor porcelain of the present invention described in claim 4, in the firing process of the barium titanate series semiconductor porcelain with positive resistance temperature characteristics, in the cooling process after reaching the highest firing temperature, at 1100 Keep at ~1200°C for 0.4 to 10 hours.

The manufacturing method of the semiconductor porcelain of the present invention described in claim 5, in the firing process of the barium titanate series semiconductor porcelain with positive resistance temperature characteristics, in the cooling process after reaching the highest firing temperature, at 1100 Slowly cool at a cooling rate of less than 1.0°C/min between ~1200°C.

According to the semiconductor porcelain of the present invention, its impulse withstand voltage characteristic can be improved by changing the distribution of its resistance value in the thickness direction.

According to the manufacturing method of the semiconductor ceramics of the present invention, by slowly cooling or maintaining the temperature during the cooling process, the semiconductor ceramics have different resistance value distributions in the thickness direction, thereby improving their impulse withstand voltage characteristics.

Fig. 1 is the pattern diagram of the variation of the resistance value per unit thickness from one main surface to the other main surface of the positive temperature coefficient thermistor obtained according to the semiconductor porcelain of the present invention;

Fig. 2 is the relationship figure that represents the resistance value ratio and the impulse withstand voltage characteristic of semiconductor ceramics of the present invention;

Fig. 3 is a graph showing the relationship between the temperature and the impulse withstand voltage characteristics of the semiconductor porcelain of the present invention during the cooling process.

An embodiment of the present invention will be described below.

First, weigh BaCO ₃ , SrCO ₃ , Pb ₃ O ₄ , CaCO ₃ , TiO ₂ , Er ₂ O ₃ , MnCO ₃ and SiO ₂ so that their composition becomes: (Ba _0.536 Pb _0.08 Sr _0.20 Ca _0.18 Er _0.004 ) TiO ₃ +0.004Mn+0.02SiO ₂ . The composition, pure water and zirconia beads were put into a polyethylene pot, pulverized and mixed for 5 hours, dehydrated, dried, and calcined at 1150° C. for 2 hours to obtain calcined powder. This calcined powder was put into a polyethylene pot together with pure water and zirconia beads, and pulverized for 5 hours. Then, it is mixed with a binder of the vinyl acetate resin series to create a granular form.

Next, a forming body with a diameter of 18 mm and a thickness of 6.3 mm was formed by a dry press, fired at 1360° C. for 1 hour, and then cooled under the conditions shown in Table 1 to obtain semiconductor ceramics. On both sides of the obtained semiconductor ceramics, electroless nickel plating is used to form a nickel layer with resistive properties as a terminal electrode, and silver paste is coated on the outermost layer, and it is dried at 600 ° C for 30 minutes to obtain a thermal conductivity with a positive temperature coefficient. Sensitive resistance.

The cooling conditions shown in Table 1 represent the conditions for cooling from the highest firing temperature to room temperature. Sample Nos. 1 to 26 represent cooling from the highest firing temperature in proportion to the cooling rate, and maintain the temperature at the holding temperature. time, then cooled from holding temperature to room temperature.

In addition, sample numbers 27 to 30 represent cooling from the highest temperature to 1200°C in proportion to the cooling rate, and between 1200 and 1100°C, cooling in proportion to the slow cooling rate, and then cooling from 1100°C to room temperature.

In addition, samples 31 and 32 represent cooling at a constant cooling rate from the highest temperature to room temperature. Table 1 Sample No. Cooling rate (℃/min) Xu cold condition Keep temperature(℃) Hold time (hours) Slow cooling speed (℃/min) 1* 3 1300 1 - 2* 3 1280 1 - 3* 3 1260 1 - 4* 3 1240 1 - 5* 3 1220 1 - 6* 3 1200 0.2 - 7 3 1200 0.4 - 8 3 1200 1 - 9 3 1200 1O - 10* 3 1200 15 - 11 3 1180 1 - 12 3 1170 1 - 13* 3 1160 0.2 - 14 3 1160 0.4 - 15 3 1160 1 - 16 3 1160 10 - 17* 3 1160 15 - 18 3 1140 1 - 19 3 1120 1 - 20* 3 1100 0.2 - twenty one 3 1100 0.4 - twenty two 3 1100 1 - twenty three 3 1100 10 - twenty four* 3 1100 15 - 25* 3 1050 1 - 26* 3 1000 1 - 27 3 - - 0.1 28 3 - - 0.5 29 3 - - 1.O 30* 3 - - 2.O 31* 1.6 - - - 32* 3 - - -

The resistivity, the resistance value per unit thickness, the impulse withstand voltage characteristic, and the resistance value ratio of the positive temperature coefficient thermistor were measured. Here, the above-mentioned impulse withstand voltage characteristic is a value obtained by the following equation; the resistance value ratio is the maximum resistance value between the surface part and the center part of the positive temperature coefficient thermistor and the maximum resistance value of the positive temperature coefficient thermistor. The ratio of the minimum resistance value at the center.

Impulse withstand voltage characteristics = (breakdown voltage) ² / resistance value at room temperature

Table 2 shows the above measurement results. Among them, the representation with ★ mark is not within the scope of the present invention, while the representation without ★ mark is within the scope of the present invention. Table 2 Sample No. ResistivityΩ·cm Impulse withstand voltage characteristics (kW) Resistance ratio 1* 50.86 13.00 1.05 2* 49.13 12.00 1.02 3* 51.44 15.00 1.08 4* 47.97 16.00 1.08 5* 51.44 28.00 1.11 6* 29 20.00 - 7 35 40.00 - 8 53.75 42.00 1.15 9 70 44.00 - 10* 100 28.00 - 11 58.96 43.00 1.36 12 54.91 51.00 1.41 13* 20 18.00 - 14 25 46.00 - 15 31.79 48.00 1.53 16 48 48.00 - 17* 58 29.00 - 18 23.12 48.00 1.68 19 26.01 47.00 1.52 20* 18 21.00 - twenty one 20 39.00 - twenty two 28.90 48.00 1.45 twenty three 40 46.00 - twenty four* 44 25.00 - 25* 31.79 23.00 1.06 26* 30.06 24.00 1.08 27 100 45.00 - 28 60 48.00 - 29 40 45.00 - 30* 35 30.00 - 31* 57.80 22.00 1.02 32* 28.90 21.00 1.05

FIG. 1 schematically shows the change in the resistance value per unit thickness from one main surface to the other main surface of the positive temperature coefficient thermistor of the present invention. As can be seen from FIG. 1 , the characteristic of the positive temperature coefficient thermistor is that the resistance value between the center part and both surface parts is low, and the resistance value between the center part and both surface parts is high.

Fig. 2 is a graph showing the relationship between the resistance value ratio and the impulse withstand voltage characteristic. In Fig. 2, it is shown that the resistance value between the surface part and the center part is higher than the resistance value of the center part by 15 to 68% (resistance value ratio is 1.15 to 1.68) and the result of excellent impulse withstand voltage characteristics of semiconductor ceramics.

Figure 3 shows the relationship between the maintenance temperature and the impulse withstand voltage characteristics during the cooling process. It can be known from Figure 3 that the temperature maintained in the cooling process is in the range of 1100-1200°, and the impulse withstand voltage characteristics are better. Also, in this temperature range, even if it is slowly cooled, its impulse withstand voltage characteristic is excellent.

The semiconductor porcelain of the present invention has excellent withstand voltage characteristics by making the distribution of the resistance value per unit thickness different, so that it will not be destroyed even under high voltage.

In addition, since the resistance value between the surface part and the center part of semiconductor ceramics is 15-68% higher than that of the surface part or the center part, the ceramics will not be damaged even for high voltage, so it is suitable for overcurrent protection of circuits .

Also, since the semiconductor ceramics of the present invention are made of barium titanate series semiconductor ceramics containing lead oxide, strontium oxide, and calcium oxide, the resistance value between the surface part and the central part of the semiconductor ceramics is higher than that of the surface part or the central part. The resistance value is 15-68% higher, the effect is more significant, and the porcelain will not be damaged for high voltage, so it can be widely used in over-current protection and demagnetization of circuits.

According to the manufacturing method of the semiconductor ceramics of the present invention, the resistance value distribution per unit thickness of the semiconductor ceramics is made different by slow cooling or maintaining the temperature in the cooling process, so that even if a high voltage is applied, the ceramics are not easily broken, and the impact withstand voltage Semiconductor porcelain with excellent characteristics.

Claims (5)

1. the semiconducting ceramic with barium titanate series of positive resistance-temperature characteristic is characterized in that, the surface element of described semiconducting ceramic and the resistance value between the central part are higher than the resistance value of the surface element or the central part of described semiconducting ceramic.

2. semiconducting ceramic as claimed in claim 1 is characterized in that, the resistance value of the surface element of described semiconducting ceramic and more described surface element of the resistance value between the central part or described central part is high by 15～68%.

3. semiconducting ceramic as claimed in claim 1 or 2 is characterized in that, described semiconducting ceramic is the semiconducting ceramic that contains the barium titanate series of plumbous oxide, strontium oxide, calcium oxide.

4. the manufacture method of a semiconducting ceramic, it is characterized in that, in the firing process of the semiconducting ceramic of the barium titanate series that will have positive resistance-temperature characteristic, in the temperature-fall period after reaching maximum sintering temperature, between 1100～1200 ℃, kept 0.4～10 hour.

5. the manufacture method of a semiconducting ceramic, it is characterized in that, in the firing process of the semiconducting ceramic of the barium titanate series that will have positive resistance-temperature characteristic, in the temperature-fall period after reaching maximum sintering temperature, between 1100～1200 ℃, cooling rate is set at is less than 1.0 ℃/min, to carry out Xu Leng.

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