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

Mg_2Si是一种环境友好的半导体材料，在500 ~ 800 K温度范围内是一种很有前途的热电材料。采用垂直布里奇曼法，在石英坩埚、氧化铝坩埚、SiNx涂层石英坩埚、CVD热解石墨坩埚CVD SiC涂层石墨，以最大限度地减少熔融Mg-一致结晶源自Mg 2Si的化学计量熔体，而不一致结晶源自Mg：Si比为85：15、70：30和60：30的非化学计量熔体。40.通过X射线衍射和电子探针显微分析来表征生长的样品，功率因数由Seebeck系数和电-从室温到773 K测量的电导率。生长的晶体是单晶，并在未掺杂的条件下表现出n型导电性。采用化学计量比熔体制备的样品的Seebeck系数为-470 mV/K，而采用Mg：Si = 70：30的非全等熔体制备的样品在373 K时的功率因数最高，为1.1 × 10 -5 W/cmK 2。

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.