INFLUENCE OF Sb- AND Al CONTENT ON THERMOELECTRIC PROPERTIES OF Sb-DOPED Mg2Si SYNTHESIZED IN Al2O3 CRUCIBLES

In this research, the effect of Sb-doping amount on Mg2Si, obtained by melting of the elements in Al2O3 crucibles was investigated. An Al-uptake originated from alumina crucibles with consequent material doping, as the reaction Mg+Al2O3->2Al+3MgO is thermodynamically favoured. The charge carrier concentration can be adjusted adding appropriate Sb amounts, leading to a reproducible synthesis of Sb:Mg2Si materials using cheap and industrial available Al2O3 crucibles. The so-obtained polycrystalline Sb-doped Mg2Si were crushed and consolidated via spark plasma sintering, obtaining dense pellets (>98%) with different amounts of Sb (0.1, 0.3, 0.5, 0.7, 1.0, 1.5 at %). The pellets were further annealed in order to prevent cracks during heating/cooling cycles. The structure and the composition of these materials are studied with powder X-ray diffraction, field-emission scanning electron microscopy coupled with electron dispersive spectroscopy. The functional properties (Seebeck coefficient, electrical resistivity and mobility and thermal conductivity) were evaluated in the RT-600°C range. The thermoelectric performance is then related to the composition of the different Sb-doped Mg2Si samples.