High pressure synthesis of multiple doped Mg2Si-based thermoelectric materials

High pressure high temperature technology is an effective route for preparing thermoelectric materials. In this work, a series of multi-doped Mg 2.02− x Al x Si 1−3 y Bi 2 y Sb y ( x  = 0.03, 0.06, y  = 0.005, 0.01) compounds have been prepared successfully by high pressure and high temperature method. The effects of post annealing on the microstructure and thermoelectric properties have been investigated. It is found that both electrical conductivity and thermal conductivity are significantly suppressed by annealing. Lower lattice thermal conductivities are observed in Mg 1.96 Al 0.06 Si 1−3 y Bi 2 y Sb y compounds, which should be attributed to the increased point-defects phonon scattering of Bi and Sb dopants induced by Al addition. Finally, a maximal figure of merit of 0.9 is achieved by Mg 1.96 Al 0.06 Si 0.985 Bi 0.01 Sb 0.005  at 773 K.