Off-stoichiometry effect on the thermoelectric properties of the pseudogap Heusler compounds

由于掺杂了季元，非化学计量Fe2-xV1+xAl合金具有较高的塞贝克系数和较低的电阻率。根据Seebeck系数对价电子浓度（VEC）的依赖关系，富v （x<0）合金可以得到-180 microV/K的大负值，而富fe （x<0）合金可以得到110 microV/K的良好p型材料。由于V/Al的非化学计量效应，Fe2V1+xAl1-x和Fe2VTaxAl1-x合金的塞贝克系数大，电阻率低，峰值温度向400-600 K的高温方向偏移较大。重元素Ta掺杂和非化学计量效应导致导热系数显著降低，使得在400-500 K左右的无因次优值达到ZT=0.22。

A combination of a large Seebeck coefficient and a low electrical resistivity has been obtained for the off-stoichiometric Fe2-xV1+xAl alloys owing to the doping of quaternary elements. On the basis of the valence electron concentration (VEC) dependence of the Seebeck coefficient, a large negative value of -180 microV/K can be obtained for the V-rich (x>0) alloys, whilst good p-type materials with 110 microV/K are derived from the Fe-rich (x<0) alloys. Because of the V/Al off-stoichiometry effect, a large Seebeck coefficient as well as a low electrical resistivity has also been found for Fe2V1+xAl1-x and Fe2VTaxAl1-x alloys, together with a large shift of their peak temperatures towards high temperatures of 400-600 K. The heavy element Ta doping combined with the off-stoichiometry effect leads to a significant decrease in the thermal conductivity, so that the dimensionless figure of merit reaches ZT=0.22 at around 400-500 K.