JPH07130505A - Semiconductor ceramic composition - Google Patents

Abstract

PURPOSE:To provide practical resistance-temperature characteristics for an NTC element which is used for motor start delaying and rush current suppressing for switching power supply and others. CONSTITUTION:In semiconductor ceramic components having negative resistance- temperature characteristics which comprise a rare earth transition element-based oxide having perovskite structure containing 100 to 10,000ppm of Zr added, the total quantity of 3 kinds of elements of Ba, Ca and Sr contained is less than 1,000ppm and does not exceed the quantity of Zr.

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) is 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 reason.

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,
If 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 period of 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 a function of decreasing the resistance value as the temperature rises, 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 that of spinel-based oxides near room temperature. It has a characteristic that the B constant is small and the B constant at a high temperature is large.

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]

The NTC element composed of the above-mentioned rare earth transition element-based oxide has an ABO ₃ type perovskite crystal structure, in which the rare earth element at the A site and the transition at the B site. Elements are occupied. Zr (4 values) mixed from grinding media when manufacturing this material
Replaces the transition element (trivalent) at the B site, so that the valence control increases the resistance value at room temperature. At this time, since the resistance value at high temperature does not change due to the mixing of Zr, the mixing ratio of Zr increases the rate of change in resistance value from room temperature to high temperature, resulting in a large B constant.

The present inventors have found that Zr is 10 to 100.
It has been discovered that resistance temperature characteristics suitable for practical use can be obtained when mixed in the range of 00 ppm. (Japanese Patent Application No. 05-
On the other hand, many impurities are mixed in the rare earth oxide and the transition element oxide, which are the starting materials when the present material is manufactured, and the starting materials of different manufacturing lots are mixed. If it is used, there has been a problem that the resistance temperature characteristic largely changes.

Therefore, an object of the present invention is to use an NTC for delaying the start-up of a motor and suppressing the inrush current of a switching power supply.
With regard to the device, it is to provide a device having resistance temperature characteristics suitable for practical use by finding out the content of impurities contained in the rare earth oxide and the transition element oxide.

[0010]

According to a first aspect of the present invention, there is provided a semiconductor ceramic having a negative resistance temperature characteristic, which is obtained by adding 10 to 10000 ppm of Zr to a rare earth transition element type oxide having a perovskite structure. In the composition, the total amount of the three elements Ba, Ca and Sr is 100.
It is characterized in that it is added in an amount of less than 0 ppm and not exceeding the amount of Zr.

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

[0012]

According to the present invention, in the first aspect, the rare earth transition element-based oxide having the perovskite structure contains 10 to 10% of Zr.
In a semiconductor porcelain composition having a negative resistance-temperature characteristic consisting of those added with 10000 ppm, Ba, Ca, S
the total amount of the three elements of r is less than 1000 ppm,
In addition, since the amount added does not exceed the amount of Zr, the range of the amount of impurities contained in the rare earth oxides and transition element oxides is limited, and the production lot of the starting material is greatly affected. In other words, the resistance-temperature characteristic having a small B constant near room temperature and a large B constant at high temperature can be stably obtained.

[0013]

EXAMPLES As rare earth transition element-based oxides, La ₂ O ₃ and C were used so that the molar ratio of La to Co was 0.95.
The powder of o ₃ O ₄ was weighed. Furthermore, ZrO ₂ and CaC
O ₃ powder was weighed and added so that the composition shown in Table 1 was obtained. Pure water was added to this weighed raw material, wet mixed 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 and FIG. Those marked with * in Table 1 are outside the scope of the present invention, and others are within the scope of the present invention.

The B constant is the temperature T (K) and the resistivity ρ
(Ω · cm), B = [ln ρ (T ₀ ) −ln ρ (T)] / (1 / T ₀ −1 / T) is a constant defined by the change of the resistance value with temperature. Indicates a percentage. 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 ° C) = [ln ρ (140 ℃) -ln ρ (25 ℃)] / [1 / (140 + 273.15) -1 / (25 + 273.15)] As shown in Table 1 and FIG.
When it is more than ppm, the specific resistance at room temperature becomes low and the B constant at high temperature becomes small, so that the resistance value in the temperature rising state cannot be made sufficiently small. On the other hand, the amount of Ca is 10
It can be seen that even when the content is less than 00 ppm, the B constant at high temperature becomes small when the Ca content exceeds the Zr content.

In the above examples, the case where Ca is added is taken as an example, but the present invention shows the same effect when Ba or Sr is added. Therefore, Ba, Ca, Sr
The content of each of the three elements is not a problem, but the total amount of these elements is a problem.

By the way, the rare earth transition element type oxide is not limited to the lanthanum cobalt type oxide,
The lanthanum-cobalt-based oxide is practically the best because it has a small B constant at room temperature and a large increase in B constant due to temperature rise.

[0019]

[Table 1]

[0020]

According to the semiconductor porcelain composition according to the present invention, since the range of the amount of impurities contained in the rare earth oxide and the transition element oxide is limited, it is not affected by the manufacturing lot of the starting material and the room temperature is maintained. A resistance-temperature characteristic having a small B constant in the vicinity and a large B constant at high temperature can be stably obtained. As a result, the NTC element has a small variation in the initial resistance value due to the change of the outside air temperature, and the power consumption in the steady state can be reduced, and the start delay of the drive motor in which a large current flows and the inrush current control of the switching power supply etc. can be suppressed. Can also be supported.

[Brief description of drawings]

FIG. 1 is a resistance temperature characteristic diagram of an example of the present invention.

 ─────────────────────────────────────────────────── ─── 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 obtained by adding 10 to 10000 ppm of Zr to a rare earth transition element-based oxide having a perovskite structure, and three kinds of elements Ba, Ca, and Sr. Is less than 1000 ppm, and an amount not exceeding the amount of Zr is added to the semiconductor porcelain composition. 2. The semiconductor ceramic composition according to claim 1, wherein the rare earth transition element-based oxide comprises a lanthanum cobalt-based oxide.