Abstract
This paper describes the semi-conductive properties of flame-sprayed TiO2 and TiO2-BaTiO3 coatings and discusses about the applicability of these coatings to thermistor elements.
The following conclusions were drawn from the results of various tests.
1) Specific resistance of the coatings increased with the increase in the addition amount of BaTiO3. Then, the change of resistance with temperature was also greater; that is, the value of B (thermistor constant) increased.
2) The heat dissipation constant (k) of single TiO2 was 0.5-1; but the value increased with the increasing addition of BaTiO3 to TiO2. It reached the maximum at a certain amount of BaTiO3, and then, decreased with the increase of BaTiO3. The maximum value of k would be at 50-60 wt% of BaTiO3.
3) Coatings of low resistance with large values of B and k could be obtained by proper selection of blending ratio, temperature of heat treatment, and electrode material.
4) In almost all the cases, TiO3-based coatings exhibited negative resistance.
5) Hall coefficient of flame-sprayed TiO2 was extremely small so that it could not be measured by the ordinary direct-current method.
