Development of the discrete electric power-generator from exhaust or waste heat sources using ecologically friendly semiconductors

Mg2Si是一种生态友好型半导体，在500至800 K的温度范围内是一种很有前途的热电材料。采用垂直Bridgman法在石英、氧化铝、sinx包覆石英、CVD热解石墨、CVD sic包覆石墨等多种坩埚中生长Mg2Si晶体，以减少生长过程中熔融Mg-Si的反应和粘附。在Mg: Si比为85:15,70:30和60:40的非化学计量Mg2Si熔体中得出了不一致结晶。通过x射线衍射和电子探针微分析对生长样品进行表征，并根据室温至773 K范围内的塞贝克系数和电导率计算其功率因数。生长的晶体为单晶，在未掺杂条件下具有n型电导率。来自化学计量熔体的样品的塞贝克系数为-470 mV/K，而来自Mg: si70:30的不一致熔体的样品在373 K时的功率因数最高，为1.1x10-5 W/cmK2。石墨基坩埚的使用，如热解石墨和SiC涂层石墨，使碳在生长的晶体中结合，导致塞贝克系数和电导率的增加。

Mg2Si, an ecologically friendly semiconductor, is a promising thermoelectric material at temperatures ranging 'rom 500 to 800 K.Mg2Si crystals were grown by the vertical Bridgman method in various crucibles made of quartz, alumina, SiNx-coated quartz, CVD pyrolytic graphite, CVD SiC-coated graphite in order to minimize the reaction and sticking of molten Mg-Si during growth.Congruent crystallization was derived from a stoichiometric melt of Mg2Si and incongruent crystallization was derived from nonstoichiometric melts having Mg : Si ratios of 85 : 1 5, 70:30, and 60:40.Grown samples were characterizedby x-ray diffraction and electron-probe microanalysis, and their power factors were calculated from the Seebeck coefficients and electrical-conductivities measured from room temperature to 773 K.The grown crystals were single crystal and showed n-type conductivity in undoped condition. A sample derived from a stoichiometric melt had a Seebeck coefficient of -470 mV/K, while the highest power factor, 1.1x10-5 W/cmK2 at 373 K, was obtained for the sample derived from an incongruent melt with an Mg : Siratio of 70:30.The use of the graphite based crucibles such as pyrolytic and SiC coated graphites caused the carbon incorporati in the grown crystals, resulting in an increase in the Seebeck coefficient and the electrical conductivity.