Structural and thermoelectric properties of porous /spl beta/-FeSi/sub 2/ prepared by thermal spraying and sintering

In this study the effect of porosity in /spl beta/-FeSi/sub 2/ on structural and thermoelectric properties was investigated for the large-scale thermoelectric power generation with porous FeSi/sub 2/ thermoelectric devices prepared by thermal spraying and sintering. In order to acquire high porosity in the silicide by sintering, an organic compound such as polyethylene glycol, sodium lauryl sulfate and polymethyl methacrylate was mixed with 1.4-/spl mu/m FeSi/sub 2/ particles, and then the mixture was sintered. The effects of the organic compounds and their amount on structural and thermoelectric properties of /spl beta/-FeSi/sub 2/ were evaluated based on SEM observation of the surface as well as on measurements of density, thermal and electric conductivity, and Seebeck coefficient. It was found that the porosity of the silicide increased up to 0.5 by adding the organic compounds, while the maximal porosity prepared by thermal spraying was at most 0.2. The heat conductivity of the porous material was found to significantly decrease down to one-tenth of that prepared by thermal spraying. Seebeck coefficient of the sintered FeSi/sub 2/ was found to be larger than that of the thermal-sprayed silicide. The pore size at the surface of the porous silicide was found to depend on the organic compounds.