JP3307732B2 - Resistive material and resistivity control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance material, and more particularly to a material for electric heating, having a resistivity of 10 ^-4 to 10 ⁵ Ω · cm.
And materials that can be controlled over a wide range, and their manufacturing methods. This resistance material can be used in fields such as home appliances, food, powder, and the chemical industry.

[0002]

^2. Description of the Related Art The amount of heat of electric heating is (current) ² × (resistance)
It is well known that the resistance is (resistivity) × (length of resistor) / (cross-sectional area of resistor). The resistivity is a physical property inherent to the material, and the required amount of heat can be obtained by changing the length and the cross-sectional area. On the other hand, when it is desired to input a necessary amount of heat to a limited surface area, that is, when a power density is specified, it is more convenient to use a material having an appropriate resistivity.

[0003] However, metal-based materials are of the order of 10 ^-4 Ω · cm, which are too small, and ceramic-based heating elements, for example, SiC, are 10 ⁰ to 10 ^-2 Ω · cm, but are inconvenient due to their positive and negative temperature coefficients. It is. There is also a method of apparently controlling the resistivity by mixing a metal and an insulator. However, as the number of insulators increases, the discontinuity becomes electrically discontinuous, and there is a drawback that reliability is increased. There is also a mixture containing carbon based on the same concept, but there is concern about safety as a heating element. In addition, a substance obtained by mixing materials having several orders of different resistivity has a lack of stability because it is said that a sudden change occurs at a certain composition according to the percolation theory.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resistive material capable of controlling the resistivity over a wide range in order to solve the above-mentioned problems of the prior art and adapt to the power density. An object of the present invention is to provide a method for controlling the resistivity using the method.

[0005]

In order to solve the above problems SUMMARY OF THE INVENTION In the present invention, _{wherein, La 1-x Ba x CoO} 3 and _{wherein, Ba 1-y La y TiO} 3 ( where, x is 0. 5 above, y is obtained by a resistive material consisting of a mixture of 1 or less). Further, in the present invention, method of producing the resistor _material, and La _{0.5 Ba 0.5} CoO ₃ BaTiO
The powder ₃ is mixed in a range of molar ratio 0.05 to 0.95, in which was be prepared by reacting at elevated temperature.

In the above production method, the reaction temperature is 800
The range of ~ 1500C is good. Further, in the above-mentioned resistance material, since the resistance materials having different resistivity can be obtained by respectively changing the molar ratios of the raw materials, the resistivity can be controlled by arbitrarily using them.

[0007]

[Action] before the reaction mixture ratio, La _0.5 Ba _0.5 CoO ₃ 0.4, a BaTiO ₃ was reacted with 0.6 and the product was subjected to X-ray diffraction. X-ray diffraction pattern is orthorhombic La
_The analysis was performed as a mixture of _0.5 Ba _0.5 CoO ₃ system and tetragonal BaTiO ₃ system. Table 1 shows the lattice constant of the resulting sintered body.

[0008]

[Table 1]

[0009] From this _result, La _{0.5 Ba} 0.5 C
In the case of oO ₃ , La having a larger ionic radius than La replaced La and the lattice constant increased, so that La _{1 -x} Ba _x
X of CoO ₃ is 0.5 or more, and Ba of BaTiO ₃ partially replaces La with Ti ^{4+ to} become Ti ³⁺ ,
It was presumed that the lattice system changed and the crystal system was changed to cubic. _Therefore, y of the Ba _1-y La _y TiO ₃ is below 1 or less. The resistance coefficient of metal or semiconductor is
The former "positive", while the latter is Ru "negative" der, resistive material of the present invention
Among the materials , those produced at a mixing ratio of BaTiO ₃ of 0.1 to 0.2 are characterized by the fact that the temperature coefficient of resistance hardly changes.

[0010]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Example 1 La _0.5 Ba _0.5 CoO ₃ and BaTiO as starting materials
I chose ₃ . The former has a resistivity of 10 ⁻⁴ Ω · cm (room temperature), and the latter has a resistivity of 10 ¹² Ω · cm. In the present study, a material having a PTCR effect by controlling the valence was used. La
_0.5 Ba _0.5 CoO ₃ was prepared from a nitrate aqueous solution of a constituent metal by coprecipitation and solid-phase reaction (1150 ° C., 12 h). BaTiO ₃ is made of BaTiO (C ₂ O ₄ ) .4H
1150 obtained by adding 0.2 mol% of Sb ³⁺ to ₂ O
It was prepared by heat treatment at 6 ° C. for 6 hours. The respective powders are mixed well at a predetermined molar ratio, and then pressure-molded (3 t / c
After m ² ), sintering was performed at 1350 ° C. for 1 hour. 5 sintered bodies
After shaping to × 3 × 15 mm, the resistivity was measured by a DC four-terminal method.

La _0.5 Ba _0.5 CoO ₃ and BaTiO ₃
Of 10: 0, 9: 1, 7: 3, 5: 5, 4:
6, 8: 2 and 0:10. Measurement of resistivity is 20
Performed at ~ 250 ° C. FIG. 1 shows the sample resistivity measured by the DC four-terminal method. Except for BaTiO ₃ whose valence is controlled
The mixing ratio between ogρ and BaTiO ₃ became linear. La
_0.5 Ba _0.5 CoO ₃ shows metal conductivity within the measurement temperature range, but became a semiconductor when the mixing ratio of BaTiO ₃ became 0.3 or more. The numerical values in the figure are the mixing ratios of BaTiO ₃ . FIG. 2 shows an X-ray diffraction pattern at a BaTiO ₃ mixing ratio of 0.6.

[0012]

The resistance material of the present invention has a resistivity of 10 ^-4 to 10 ^-4 .
Since a resistivity of 10 ⁵ Ω · cm is obtained, and the logarithm of the resistivity has a linear relationship with the composition, the resistivity can be controlled according to the purpose and can be effectively used in each field.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between temperature and resistivity when the mixing ratio is changed.

FIG. 2 is an X-ray diffraction pattern diagram with a BaTiO ₃ mixing ratio of 0.6.

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP-B-58-33191 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C ^7/ 00-17/30

Claims (4)

(57) [Claims] 1. The formula, La _1-x Ba _x CoO _3, and the formula:
_{Ba 1-y La y TiO 3} ( where, x is 0.5 or more,
y consists of a mixture of 1 or less) resistive material. 2. La _0.5 Ba _0.5 CoO ₃ and BaTiO
_{3. The} method for producing a resistance material according to claim 1, wherein the powder is mixed with a powder having a molar ratio of 0.05 to 0.95 and reacted at a high temperature. 3. The method according to claim 2, wherein the reaction temperature is 800 to 1500 ° C. 4. The resistivity control method according to claim 1, wherein the component ratios are changed to produce materials having different resistivity.