Development of environmental conservation type thermoelectric device of silicide compounds and their power generation modules

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Recently, thermoelectric materials are attracted as an energy-conversion technology between thermal energy and electric energy directly, and are possible to utilize low-grade energy, i.e. waste heat at middle- and the low-temperature. At present, Bi_2Te_3, CoSb_3 and SiGe are principally investigated and applied. These compounds, however, are composed of poisonous, limit in resource, and/or expensive elements. Therefore, the application of these materials is restricted, and also the use of these materials will be controlled in the near future in order to the pollution abatement of environment. In this study, thermoelectric materials composed of atoxic and resource-rich elements were developed, and investigated the effect of the dopant on the thermoelectric properties. The results obtained in this study are as follows.1. In Al-doped Mg_2Si compounds, the maximum figure of merit of 0.67×10^<-3> K^<-1> was obtained at 856 K for the specimen with nominal Al content of 0.15 at%. The obtained figure of merit is comparable to that reported for Si-Ge, suggests that Al doped Mg_2Si is a good candidate material for thermoelectric energy conversion in the middle-temperature range.2. Fe_2VAl_<0.95>Si_<0.05> compound showed a high power factor value of 3.1×10^<-3> Wm^<-1>K^<-2>. This value is comparable that of Bi_2Te_3 known as the best thermoelectric materials in the low-temperature range. This suggests that Si doped Fe_2VAl compounds is a good candidate thermoelectric material in the low-temperature range.3. Al-doped Mg_2Si and Si doped Fe_2VAl compounds are n type. The development of highly efficiency p type thermoelectric materials is needed.