抄録
In the previous paper, the semi-conductive properties of titanium oxide coatings were explained in terms of oxygen deficiency and gradients of oxygen concentration within the coatings. In order to prove this hypothesis, the coatings were examined with X-ray diffractometer, micro-analyzer, thermal analyzer, etc.. The following conclusions were drawn from the results of these analyses.
The flame sprayed TiO2 powder mainly comprised rutile crystals containing small amounts of anatase and brookite. The flame sprayed coatings of titanium oxide were composed of multi-components, including rutile, brookite, anatase, Ti3O5, Ti2O3, TiO, ete.. In addition to the above components, the coatings of BaTiO3-TiO2 system contained glassy BaTiO3.
Heat treatment of the coatings promoted the crystallization, but lattice parameters of rutile were not varied; whereas, tetragonality of BaTiO3 was steadily increased with the rise of treating temperature.
The dispersions of Ti and Ba were rather good, but that of oxygen was not good. The concentration of oxygen was made uniform by the heat treatment.
Direct heat treatment in the air gave steep gradients of oxygen concentration; but the concentration within the coatings was made uniform by the heat treatment of the coatings covered with carbon.
A steep gradient oxygen concentration was produced near the surface of the coatings by means of a fired-on silver electrode.
Flame sprayed TiO2 coatings had about 1.3wt% of oxygen deficiency; while the deficiency in TiO2-BaTiO3 coatings was only 0.2wt%, which depended on the ratio of TiO2 to BaTiO3. The degree of oxygen deficiency in the coatings was decreased by heat treatment.
