JPH07106107A - Ceramic semiconductor composition - Google Patents

Abstract

PURPOSE:To provide an NTC device having an appropriate temperature coefficient of resistance and suitable for applications such as the suppression of the delay in start of a motor or the rush current of a switching power source, etc. CONSTITUTION:A ceramic semiconductor composition having a negative temperature coefficient of resistance comprises a rare earth transition element oxide having perovskite structure, and the mol ratio between the rare earth element and the transition element is 0.60-1.10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor ceramic composition having a negative resistance temperature characteristic.

[0002]

2. Description of the Related Art Conventionally, an element having a negative resistance temperature characteristic (NTC element) has been used as an element for delaying the start-up of a drive motor or suppressing an inrush current in a switching power supply.
This is due to the following reasons.

In a gear device configured to start the supply of lubricating oil only after the motor is started, if the drive motor immediately rotates the gear device at a high speed, the supply of lubricating oil becomes insufficient and the gear may be damaged. There is. Also, the lap plate that grinds the porcelain surface by rotating the grindstone,
When the grindstone is rotated at a high speed at the moment when the drive motor is activated, the porcelain to be ground may be broken. In order to avoid such a problem, it is necessary to delay the activation of the drive motor for a certain time until the gear and the grindstone rotate at high speed. Further, in the switching power supply, since an overcurrent flows at the moment when the switch is turned on, it is necessary to absorb this initial inrush current.

By the way, the NTC element has a high resistance value at room temperature and has a function of decreasing the resistance value with an increase in temperature, and is composed of a spinel oxide or a rare earth transition element oxide. .

In particular, the rare earth transition element-based oxides have a temperature dependence in the ratio of the resistance value (B constant) that decreases with an increase in temperature, which is higher than the spinel-based oxides at around room temperature. Has a small B constant and a large B constant at high temperature.

Therefore, the NTC element composed of the rare earth transition element-based oxide has a small variation in initial resistance value due to a change in outside air temperature, can reduce power consumption in a steady state, and can drive a large current. It is also used in motors and switching power supplies.

[0007]

By the way, an NTC element composed of a rare earth transition element-based oxide has an ABO ₃ type perovskite crystal structure, in which a rare earth element is present at the A site and a transition is made at the B site. Elements are occupied. In the material having the perovskite crystal structure, it is general that the molar ratio of the A site element and the B site element greatly affects the characteristics. The resistance temperature characteristics of the rare earth transition element-based oxide are buoy. Gee. Bhide (VGBh
ide) and Dee. S. It has been investigated by DS Rajoria et al. (Phys.Rev.B6 [3] 1021 (1972)) However, confirmation of the characteristics obtained when the molar ratio of rare earth element and transition element was changed, and it was used to suppress the start delay of the motor and the inrush current of the switching power supply etc. Practical tests of applicability have never been performed.

Therefore, an object of the present invention is to use an NTC for delaying the start-up of a motor and suppressing an inrush current of a switching power supply or the like.
With regard to the device, it is to provide a device in which a resistance temperature characteristic suitable for practical use can be obtained by finding a molar ratio of a rare earth element and a transition element.

[0009]

According to a first aspect of the present invention, in a semiconductor porcelain composition having a negative resistance temperature characteristic composed of a rare earth transition element-based oxide having a perovskite structure, the rare earth element and the transition element are The molar ratio (rare earth element / transition element) is 0.60 to 1.10.

In the second aspect, the rare earth transition element-based oxide of the semiconductor ceramic composition according to the first aspect is a lanthanum-cobalt-based oxide.

The molar ratio of rare earth element to transition element is 0.60.
If it is lower than or higher than 1.10, the resistance value in the temperature rising state does not become sufficiently small, so that the power consumption in the steady state increases and it cannot be used in a place where a large current flows.

The rare earth transition element type oxide is not limited to the lanthanum cobalt type oxide, but when the lanthanum cobalt type oxide is adopted, the B constant at room temperature is small and the temperature rises. It is practically the best because the B constant increases greatly.

[0013]

According to the first aspect of the present invention, in a semiconductor porcelain composition having a negative resistance temperature characteristic comprising a rare earth transition element-based oxide having a perovskite structure, the molar ratio of rare earth element to transition element (rare earth element / Transition element) to 0.
Since 60 to 1.10, the molar ratio of the rare earth element to the transition element is in the optimum range, and the resistance-temperature characteristic that the B constant at room temperature is small and the B constant at high temperature is large is obtained.

[0014]

Example As a rare earth transition element-based oxide, La was prepared so that the molar ratio of La to Co was 0.50 to 1.20.
The powders of ₂ O ₃ and Co ₃ O ₄ were weighed in the ratios shown in Table 1. Then, this weighed raw material was wet mixed with pure water in a ball mill for 10 hours, dried and calcined at 1000 ° C. for 2 hours. A vinyl acetate binder was added to this calcination raw material, and the mixture was wet mixed again in a ball mill for 5 hours, pulverized and dried, and a pressure of 2 tons was applied to a disc having a diameter of 10.0 mm and a thickness of 3.0 mm. It was formed by molding. 5 this molded body
After degreasing at 00 ° C., it was fired in air at 1400 ° C. for 2 hours to obtain a sintered body. Next, after applying a platinum paste to both main surfaces of this sintered body, it was baked at 1000 ° C. for 10 minutes to form an external electrode to obtain an NTC element.

The resistance temperature characteristics of the obtained NTC element are shown in Table 1. Those marked with * in Table 1 are outside the scope of the present invention, and others are within the scope of the present invention.

B constant is T (K) for temperature and ρ for specific resistance.
(Ω · cm), B = [ln ρ (T ₀ ) −ln ρ (T)] / (1 / T
It is a constant defined by _0-1 / T) and indicates the rate of change in resistance value with temperature. The larger this value, the larger the rate of change in resistance value with temperature. B (-10 ° C) and B (14 in Table 1)
0 ° C.) was determined as follows.

B (-10 ° C) = [ln ρ (-10 ° C) -ln ρ (25 ° C)] / [1
/(-10+273.15)-1/(25+273.15)] B (140 ℃) = [ln ρ (140 ℃) -ln ρ (25 ℃)] / [1 / (140 + 273.1
5) -1 / (25 + 273.15)] As is clear from Table 1, when the molar ratio of La to Co is in the range of 0.60 to 1.10, the B constant at high temperature is large and The resistance value of can be made sufficiently small. On the other hand, when the molar ratio of La to Co is lower than 0.60 or higher than 1.10, the B constant at high temperature becomes 3000 K or less, and the resistance value in the temperature rising state cannot be sufficiently reduced.

In the above examples, the case where the lanthanum cobalt-based oxide was used was taken as an example, but the present invention is also applicable to the case where lanthanum such as neodymium cobalt-based oxide is replaced with another rare earth element. Therefore, it is possible to obtain the characteristics required for delaying the start-up of the motor and suppressing the inrush current in the switching power supply.

[0019]

According to the semiconductor porcelain composition according to the present invention, since the molar ratio of the rare earth element and the transition element in the rare earth transition element-based oxide is optimized, the B constant near room temperature is small and the B constant at room temperature is high. A resistance temperature characteristic having a large B constant can be obtained. As a result, the NTC element has a small variation in the initial resistance value due to changes in the outside air temperature, can reduce the power consumption in the steady state, and can also suppress the startup delay of the drive motor in which a large current flows and the inrush current of the switching power supply. Can handle.

[0020]

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunizaburo Banno 2 26-10 Tenjin Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A semiconductor porcelain composition having a negative resistance temperature characteristic, which is composed of a rare earth transition element-based oxide having a perovskite structure, and has a molar ratio of rare earth element to transition element (rare earth element / transition element) of 0.60. 1. The semiconductor porcelain composition characterized in that 2. The semiconductor ceramic composition according to claim 1, wherein the rare earth transition element-based oxide comprises a lanthanum cobalt-based oxide.