抄録
Semi-conductive barium titanate coating could be formed merely by flame spraying of barium titanate powder containing several wt. % of metal oxides. The additives giving the lowest resistivity of coatings (the order of 10-102ohm-cm) found at present included oxides of Sm, Nd, Ta and Nb. The minimum amounts of these oxides giving the lowest resistivity were generally in the range of 1.5-2.5wt. %, according to their kind, which were much larger than those in ceramic barium titanate.
The PTC (Positive Temperature Coefficient) of resistance was observed for some kinds of oxides, but generally the gradient of resistance change with temperature was much slower than that in the conventional ceramic barium titanate.
Heat treatment improved conductivity to a large extent and decreased the gradient of resistivity change with temperature for most of the oxides. The conduction mechanism is now believed to be the combination of valence control and a lattice defect such as oxygen defect for producing conductivity.
The values of activation energy were varied in a wide range (within 0.01-0.35eV) according to kind of additives, conditions of heat treatment, and other factors.
