JPH0684605A - Positive characteristic thermister and production thereof - Google Patents

Abstract

PURPOSE:To obtain a positive characteristic thermister in which nominal zero load resistance is lowered without sacrifice of withstand voltage. CONSTITUTION:In the composition (Ba1-X-Y'SrX, CaY)aTibO3 or positive characteristic thermister(where. 0<=X<=0.3, 0<=Y<=0.3), quantity of barium is increased or quantity of titanium is decreased to set the ratio a:b at 1.0003:1-1.001:1 thus lowering withstand voltage as compared with a positive characteristic thermister having the ratio of a:b equal to 1:1 and obtaining a positive characteristic thermister having low nominal zero load resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor having a positive resistance temperature characteristic (hereinafter referred to as PTC characteristic), and to a positive characteristic thermistor having a reduced nominal zero load resistance value (standard resistance value at 25 ° C.). Is.

[0002]

2. Description of the Related Art PTC characteristics above the Curie point are obtained by adding trivalent rare earth metal elements such as Y and La and pentavalent transition metal elements such as Sb or Nb to barium titanate and baking them. It has been known. Utilizing this characteristic, it is used in various objects such as temperature sensors, degaussing circuit elements, overcurrent prevention circuit elements, and self-temperature control heating elements. Among such PTC thermistors, there are many standard values, and the nominal zero load resistance value is an important index.

[0003]

In order to reduce the nominal zero load resistance value, a method of reducing the amount of Mn or Si, or a method of firing in a reducing atmosphere is used. The obtained positive temperature coefficient thermistor has a problem that the withstand voltage is lower than the original value although the resistance is low. It is an object of the present invention to provide a method for manufacturing a positive temperature coefficient thermistor that reduces the nominal zero load resistance value without reducing the withstand voltage of the positive temperature coefficient thermistor as much as possible.

[0004]

The positive temperature coefficient thermistor of the present invention is (Ba _1-XY , Sr _X , Ca _Y ) _a Ti _b O.
₃ (where 0 ≦ X ≦ 0.3 and 0 ≦ Y ≦ 0.3) in the composition of the positive temperature coefficient thermistor containing the complex oxide of barium and titanium as the main component, b
Is a positive temperature coefficient thermistor whose ratio is not 1: 1, and a:
It is preferred that b has a ratio of 1.3: 1 to 1.1: 1.

The positive temperature coefficient thermistor of the present invention is manufactured by previously adjusting the composition ratio of the raw materials so that the composition ratio becomes a predetermined ratio, or by firing (Ba _1-XY , Sr).
_X , Ca _Y ) TiO ₃ (where 0 ≦ X ≦, 0 ≦ Y ≦
Is. ) (Ba _1-XY , Sr _X , Ca
_The raw material composition in which _Y ) and Ti are 1: 1 is from 1050 to 12
After calcination at 00 ° C, BaO,
It can be manufactured by adding a barium compound such as BaCO ₃ , BaI ₂ , BaF ₂ , or BaCl ₂ within a range of 0.03 to 0.10 mol% and firing at 1300 to 1400 ° C.

[0006]

[Function] In a barium titanate-based positive temperature coefficient thermistor, a positive temperature coefficient thermistor having a small nominal zero load resistance value and a small decrease in withstand voltage can be obtained by increasing the ratio of barium or decreasing the ratio of titanium. .

[0007]

EXAMPLES Examples of the present invention will be described below. Example 1 Nb ₂ O ₅ was added in an amount of 0.0005 per mol of the raw material having a composition of (Ba _0.94 , Ca _0.02 , Sr _0.04 ) TiO _3.
Mol, Sb ₂ O ₃ 0.001 mol, MnCO ₃ 0.
0007 mol and 0.002 mol of SiO ₂ were added.

This is the basic composition of barium titanate, the amount of titanium oxide is as it is, the amount of titanium oxide is 0.03 mol%, 0.05 mol%, 0.07 mol%,
After blending the compositions each reduced by 0.10 mol%, wet kneading was performed in a rubber-lined ball mill using nylon boulders. After drying, calcination was performed, wet pulverization was performed by a ball mill, and 10% by weight of 15% polyvinyl alcohol aqueous solution was added to the raw material for granulation.
The obtained granules were molded into a disk shape having a diameter of 10 mm and a thickness of 1 mm at a pressure of 1000 kg / cm ² , and then in the atmosphere,
Firing was performed at 1350 ° C. for 1 hour. Ohmic silver electrodes are baked on both sides of these sintered bodies to produce PTC thermistors, and the nominal zero load resistance value is measured with a multimeter in a thermostatic chamber. Table 1 shows the result of the measurement.

[0009]

[Table 1]

The nominal zero load resistance value was reduced by about 16%, but the withstand voltage was only reduced by about 7% due to the decrease in the mixing ratio of titanium oxide.

Example 2 0.0005 of Nb ₂ O ₅ was added per mol of the raw material having the composition of (Ba _0.94 , Ca _0.02 , Sr _0.04 ) TiO _3.
Mol, Sb ₂ O ₃ 0.001 mol, MnCO ₃ 0.
Wet-kneading was performed by adding 0007 mol and 0.005 mol of SiO ₂ to make this a basic composition of barium titanate and using nylon cobblestone in a rubber lining ball mill. After drying, calcination is performed at 1150 ° C., and barium carbonate is added to the calcined powder so that the amount of barium becomes 0.03 mol%, 0.05 mol%, 0.07 mol%, 0.10 mol%. The mixture was added and wet mixed and pulverized in a ball mill, and then 10% by weight of 15% polyvinyl alcohol aqueous solution was added to the raw material for granulation. The obtained granulated product is formed into a disk shape having a diameter of 10 mm and a thickness of 1 mm at 1000 k.
Molded at a pressure of g / cm ² and in the air at 1350 ° C
After firing for 1 hour, the nominal zero load resistance value and withstand voltage were measured in the same manner as in Example 1, and the results are shown in Table 2.

[0012]

[Table 2]

As in Example 1, the decrease in withstand voltage was small with respect to the decrease in the nominal zero load resistance value. Further, as barium sources, BaO, BaCO ₃ , BaI ₂ , BaF ₂ and B are used.
Similar results were obtained by using aCl _{2 and the} like, and the same was obtained when the composition ratio was adjusted by adding a barium source before calcination.

Example 3 (Ba _0.76 , Ca _0.02 , Sr _0.22 ) TiO ₃ as a main component Y ₂ O ₃ 0.0017 mol, MnCO ₃ 0.0
007 mol, a composition containing 0.017 mol of SiO ₂ (composition A), and (Ba _0.96 , C
a _0.01 , Sr _0.22 ) TiO ₃ and Y ₂ O as a semiconducting agent
0.0017 mol of ₃ was added, the other additives had the same composition as in Example 2 (composition B), and the main components were (Ba _0.94 , C).
a _0.02 , Sr _0.22 ) TiO ₃ , other additives are composition A
A positive temperature coefficient thermistor was manufactured in the same manner as in Example 1 by using the raw materials having the same composition (composition C) as in Example 1, the nominal zero load resistance value and the withstand voltage were measured, and the results are shown in Table 3.
Shown in.

[0015]

[Table 3]

Example 4 BaC was added to each of the calcined powders of composition A, composition B and composition C of example 3.
O ₃ was added in an amount of 0.05 mol%, a positive temperature coefficient thermistor was manufactured in the same manner as in Example 2, the nominal zero load resistance value and the withstand voltage were measured, and the results are shown in Table 4. The rate of decrease in withstand voltage was smaller than the rate of decrease in resistance as compared with the composition before addition.

[0017]

[Table 4]

[0018]

According to the present invention, (Ba _1-XY , Sr
_X , Ca _Y ) _a Ti _b O ₃ (where 0 ≦ X ≦ 0.3,
0 ≦ Y ≦ 0.3. ) By increasing the barium or decreasing the titanium, the ratio of a: b in
Preferably, by setting the ratio of a: b to 1.3: 1 to 1.1: 1, a positive temperature coefficient thermistor having a small nominal zero load resistance value and a small decrease in withstand voltage can be obtained.

Claims (3)

[Claims] 1. A barium titanate-based positive temperature coefficient thermistor comprising: (Ba _1-XY , Sr _X , Ca _Y ) _a Ti _b O
₃ (where 0 ≦ X ≦ 0.3 and 0 ≦ Y ≦ 0.3), the a: b ratio of the composition formula of the ceramics is set to 1.0003: 1 to 1.001: 1. A positive temperature coefficient thermistor. 2. A method for manufacturing a barium titanate-based positive temperature coefficient thermistor, wherein (Ba _1-XY , Sr _X , Ca _Y ) _a T is obtained by increasing the Ba component or decreasing the Ti component.
i _b O ₃ (where 0 ≦ X ≦ 0.3 and 0 ≦ Y ≦ 0.3) has a composition ratio of ceramics represented by a: b ratio of 1.0003: 1 to 1.001. 1. The method for manufacturing a positive temperature coefficient thermistor, wherein: 1. 3. An increase in the Ba component or a decrease in the Ti component is characterized by increasing the barium compound as a raw material, decreasing the titanium compound, or adding the barium compound to the calcined powder in which a: b is 1: 1. The method for manufacturing a positive temperature coefficient thermistor according to claim 2.