Microstructure and electric properties of low-pressure plasma sprayed β-FeSi2 based coatings

Thermoelectric material β-FeSi2 based coating was fabricated by the technique low-pressure plasma spray (LPPS) on the Al2O3 substrate from different alloy powders. During the process LPPS, the phase transformation had occurred through the peritectoid, eutectoid reaction and their inverse reaction. The grain size of the as-sprayed β-FeSi2 doped Co coatings was reduced comparing with the original feedstock powders, which implied the thermal conductivity could effectively decreased by the LPPS process. The room temperature electrical conductivity showed metal and semiconductor properties on the as-sprayed and annealed coatings. This method and the results could solve the problems of practical application especially on special-shaped surfaces such as the automobile exhaust pipe or other complex surface shape of the device.