JPH07211512A - Positive temperature coefficient thermistor - Google Patents

Abstract

PURPOSE:To provide a positive temperature coefficient thermistor whose positive resistance temperature coefficient just after Curie temperature is large and voltage dependency is low, in the positive temperature coefficient thermistor which is utilized for a switching element or constant-temperature heat generating body. CONSTITUTION:This thermistor element is made by adding 0.005-0.13mol of CaTiO3 to 1mol of barium titanate-based semiconductor ceramics composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive temperature coefficient thermistor having a large positive temperature coefficient of resistance immediately after the Curie temperature and used as various switching elements such as a temperature compensator or a constant temperature heating element.

[0002]

2. Description of the Related Art Conventionally, barium titanate is added to rare earth elements,
Bi, Sb, etc. were added to form a positive temperature coefficient thermistor element.

[0003]

SUMMARY OF THE INVENTION In the above conventional configuration,
The positive temperature coefficient of resistance immediately after the Curie temperature is small, and when used as a constant temperature heating element, for example, the applied voltage is 22
It has a voltage dependency at a high voltage of 0 V or higher. Therefore, the amount of heat generated by the positive temperature coefficient thermistor element differs depending on the applied voltage, and the thermistor element must be changed depending on the voltage used.

The present invention solves the above problems, and an object thereof is to provide a positive temperature coefficient thermistor having a large positive temperature coefficient of resistance immediately after the Curie temperature.

[0005]

In order to achieve this object, in the positive temperature coefficient thermistor of the present invention, the thermistor element is CaT based on 1 mol of the barium titanate-based semiconductor ceramic composition.
It is formed by adding 0.05 to 0.13 mol of iO ₃ .

[0006]

With this configuration, the crystal grain size of the thermistor element becomes uniform and small, and the thermistor element becomes dense. As a result, a positive temperature coefficient thermistor having a large positive temperature coefficient of resistance immediately after the Curie temperature and a small voltage dependence can be obtained.

[0007]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below.

First, as a barium titanate semiconductor porcelain composition, commercially available BaCo ₃ , TiO ₂ , PbO, Y ₂ O ₃ ,
Al ₂ O ₃ , SiO ₂ , Mn (No ₃ ) ₂ and CaTiO ₃ were weighed so as to have the composition shown in (Chemical formula 1), and sample No. shown in (Table 1). 1200 g of the material powders 1 to 12 were prepared.

[0009]

[Chemical 1]

[0010]

[Table 1]

Next, the sample No. 1 material powder, 2 liters of pure water and 3 kg of YTZ balls having a diameter of 10 mm were put in a 10 liter ball mill, wet-mixed for 20 hours, passed through 180 mesh and then 1
It was dried at 50 ° C. Then, the mixture is crushed into 11
What was calcined at 00 ° C. for 2 hours, 1 liter of pure water and 3 kg of YTZ balls having a diameter of 10 mm were put in a 10 liter ball mill, wet pulverized for 20 hours, and then dried at 150 ° C. Next, 10% by weight of a 5% aqueous solution of polyvinyl alcohol was added to this pulverized powder, and the mixture was granulated for 5 minutes with a liquor machine, then passed through 20 mesh and a disk with a pressure of 800 kg / cm ² was applied using a molding die having a diameter of 12 mm. It was molded into a shape. This molded body is 300 ° C
The temperature was raised to 1250 ° C. at a heating rate of 1 / hour, and the mixture was baked at 1250 ° C. for 3 hours, and then gradually cooled to room temperature at a cooling rate of 150 ° C./hour. Next, aluminum metallikon spray electrodes were provided on both surfaces of this sintered body, and sample No. Got 1. Similarly, sample
No. 2-12 were formed. For comparison, the sample No. shown in (Table 1). A conventional PTC thermistor having a composition of 13 was prepared.

The temperature coefficient of resistance of these samples was measured,
It shows in (Table 1). The temperature coefficient of resistance was measured as follows. First, the resistance value of the positive temperature coefficient thermistor with respect to the temperature change from room temperature to 300 ° C. was measured. Next, the temperature at which the resistance value is twice the room temperature resistance value is defined as the Curie temperature, and the resistance value at the Curie temperature and the resistance value at the Curie temperature + 10 ° C are obtained, and the resistance value change rate is calculated by (Equation 1). The temperature coefficient of resistance was used.

[0013]

[Equation 1]

Normally, the resistance temperature coefficient is obtained at the Curie temperature + 30 ° C., but since the present invention aims to increase the resistance temperature coefficient immediately after the Curie temperature, the resistance temperature coefficient is obtained at the Curie temperature + 10 ° C. It was calculated.

As can be seen from (Table 1), the sample No.
2 to 11 are sample numbers. Compared with the conventional example of No. 13, the positive temperature coefficient of resistance immediately after the Curie temperature is improved. Furthermore,
Figure 1 operating temperature change of the PTC thermistor when a voltage 100V is applied during and 220V is applied as shown in (a width of T ₁ -T ₂₎ is smaller than the conventional operating temperature change (range of T ₃ -T ₄₎ , It is possible to maintain an almost constant calorific value. Therefore, it is not necessary to change the positive temperature coefficient thermistor according to the used voltage as in the conventional case, and the same element can be used. However, sample No. 1, sample No. When the addition amount of CaTiO ₃ is less than 0.05 mol or exceeds 0.13 mol as in No. 12, the temperature coefficient of resistance is small as in the conventional case.

In this example, CaTiO ₃ was manufactured as follows. First, commercially available CaCo ₃ and T
90% of a mixture of iO ₂ at a ratio of 1: 1 (molar ratio)
0g was prepared. Next, this is put in a 10-liter ball mill, 2 l of pure water and 3 kg of YZT balls having a diameter of 10 mm are added, and 2
It was wet-milled for 0 hours. After that, pass 180 mesh,
What was dried at 150 ° C was roughly crushed and calcined at 1100 ° C for 2 hours. Next, put the calcined powder in a 10 l ball mill,
Add 1 liter of pure water and 3 kg of YZT balls with a diameter of 10 mm, and add 20
It was wet-milled for an hour and dried at 150 ° C. Then, CaTiO ₃ was obtained by coarsely crushing for 3 minutes with a Likai machine. But,
Even if a commercially available CaTiO ₃ is used, the effect does not change.

[0017]

As described above, according to the present invention, the positive temperature coefficient thermistor element is formed by adding 0.05 to 0.13 mol of CaTiO ₃ to 1 mol of the barium titanate-based semiconductor ceramic composition. is there. With this configuration, the crystal grain size of the thermistor element becomes uniform and small, and the thermistor element becomes dense. As a result, a positive temperature coefficient thermistor having a large positive resistance temperature coefficient immediately after the Curie temperature and a small voltage dependence can be provided.

Further, since the positive temperature coefficient thermistor element of the present invention has a large positive temperature coefficient of resistance immediately after the Curie temperature, it is possible to improve the attenuation characteristic until a stable current is reached by applying a voltage.

[Brief description of drawings]

FIG. 1 is a resistance value-temperature characteristic diagram of a positive temperature coefficient thermistor according to an embodiment of the present invention.

Claims (1)

[Claims] 1. A positive temperature coefficient thermistor element and at least a pair of electrodes provided on the surface of the positive temperature coefficient thermistor element, wherein the positive temperature coefficient thermistor element is based on 1 mol of a barium titanate-based semiconductor ceramic composition. A positive temperature coefficient thermistor formed by adding 0.05 to 0.13 mol of CaTiO ₃ .