Thermoelectric Device Fabricated by Plasma Spray

A thermoelectric power generating device, in which all components were fabricated by plasma spray technique, was manufactured and its performance was evaluated. Its basic unit was composed of (Ca,Bi)₃Co₄O₉ p-type semiconductor chip and (Sr,Y)TiO_3-x n-type semiconductor chip. The plasma sprayed (Ca,Bi)₃Co₄O₉ and (Sr,Y)TiO_3-x deposits showed the Seebeck effect according to expectation. However, the ZT values, which indicated the thermoelectric performance, were still poor because of the low electric conductivity. Measurements of some basic properties revealed that increase of the target phase content was important for the p-type material. On the other hand, decrease of the resistivity was strongly desired for the n-type material by process improvement. Power generating test was performed using pipe shape device fully fabricated by plasma spraying and the electric output was successfully obtained under a temperature gradient.