Effect of dispersion of nanosize silica fine powder on the thermoelectric properties of cobalt-doped beta-iron disilicide

The reduction of thermal conductivity of beta-iron disilicide is the key to realize thermoelectric power generation based on the material. Nanosize silica powder with the average diameter of 310 nm was dispersed in beta-iron disilicide doped with 5% cobalt. Iron disilicide and fine silica powder were mixed by ball-milling, then hot-pressed at 1100/spl deg/C, followed with post-sintering heat treatment at 848/spl deg/C for 20 h. The temperature dependencies of the physical properties such as the Seebeck coefficient, electrical conductivity, thermal conductivity were evaluated in the temperature range of 40-600/spl deg/C. The thermal conductivity decreased significantly by the fine silica dispersion. Although the electric conductivity also decreased, the thermoelectric figure of merit was improved by the decreased thermal conductivity and increased thermoelectric power.