The direct conversion of heat into electric current is still less developed form of energy conversion. Thermoelectric material working in a temperature gradient is able to induce a voltage that can drive a serial resistor. New research activities try to broaden the employment of thermoelectric generators from spacecraft technologies to terrestrial applications. The main problem at the moment is rather the lack of economic production methods, than the low efficiency of conversion. After an overview about the basics of thermoelectrics and possible applications the paper presents the thermal spraying as an alternative processing method with first attempts to realize graded structures. Al-doped and Co-doped FeSi2 has been consolidated by APS, SPS, VPS and HVOF spraying. The microstructure, phase composition and oxygen input have been investigated and set into relation to thermoelectric properties.