Effects of oxide additive on thermoelectricity of FeSi2
Thermoelectricity has been hot issue in these days, because of environmental problems and energy sources deficit. Moreover, material development for thermoelectricity is now busy in oxide and metal or alloy, basically. However, conclusive materials with good performance have not yet been found in application basis. We have studied oxide-added beta-FeSi2 for these years. Iron disilicide is well known and utilized in relatively higher temperature. In this report, we indicated our successful improvement of performance of beta-FeSi2 added with Ta2O5 showing the figure of merit almost 0.3 times 10-3/K This was obtained by reducing thermal conductivity and electrical resistivity (a half of standard FeSi2)
Effect of Electronic Structure on Seebeck Coefficient of Oxide Thermoelectric Semiconductor and Role of the Oxide
An oxide is functionally classified into two categories when regarding oxide as thermoelectricity: 1) an oxide itself has thermoelectric properties such as CaMnO3, homologous series of (ZnO)m and NaCo2O4, and they have been researched since around 1995. 2) there are researches on oxide as an additive to conventional thermoelectric material. We have investigated to approach thermoelectric property from the electronic structures by ab initio calculation. We propose to estimate Seebeck coefficient of oxide by regarding movement of electron between energy levels in the electronic structures. Thereby, it will lead to a new thermoelectric material of oxide. Furthermore, we can improve figure of merit by adding oxide to FeSi2 due to reducing thermal conductivity in the present study.
Hopping carrier mobilities and thermoelectric properties of oxide materials with perovskite-related structure
Thermoelectric properties of perovskite-type oxides are investigated with particular interests in their hopping carrier mobility. A series of partial substitution for metal cations in CaMnO/sub 3/, a perovskite-type oxide showing small polaron hopping conduction, reveals that larger substituents for both Ca and Mn sites result in higher carrier mobilities. Consequently, Bi and In attain the largest ZT values for the Ca and Mn site substitutions, respectively. Increase in the hopping intersite distance is suggested as a reason of the enhanced mobilities. As a consequence, the largest substituent for the Mn site, In, gives the highest mobility, and thereby brings about the largest power factor for Ca(Mn/sub 0.9/In/sub 0.1/)O/sub 3/. Also benefiting from the fairly low thermal conductivity, the In-substituted sample attains ZT=0.16 at 900/spl deg/C.