An improvement of thermoelectric properties for Mg₃Bi₂/Mg₂Sn nanocomposite films by the phase interface

Mg3Bi2/Mg2Sn nanocomposite films were prepared on single Si substrate using high pure metal Mg, Mg3Bi2 and Mg2Sn target by alternately sputtering. The phase composition of the deposited Mg3Bi2/Mg2Sn films was analyzed by X-ray diffraction patterns. The surface and cross-sectional morphology of the deposited Mg3Bi2/Mg2Sn films was observed by scanning electron microscope. The content and distribution of elements in the deposited Mg3Bi2/Mg2Sn films were measured by an energy dispersive spectroscopy. The Seebeck coefficient and electrical conductivity of the deposited films was measured by Seebeck coefficient/resistance analysis system. The carrier concentration and carrier mobility of the sample was measured and calculated by Hall experiments. Results showed that the Mg3Bi2/Mg2Sn films were composed of Mg3Bi2, Mg2Sn and a few of metal Mg phase. The carrier (hole) concentration and Seebeck coefficient gradually increased, but the mobility and electrical conductivity decreased with increasing the Mg2Sn phase content in deposited films. As a result of the competition between the electrical conductivity and the Seebeck coefficient, the power factor first increased, reached a maximum value of 1.20 mWm(-1)K-2 at 155 degrees C, and then decreased. The deposited Mg3Bi2/Mg2Sn nanocomposite films with 6.5 at.% Sn possessed the highest power factor in measured temperature range. The power factor of deposited Mg3Bi2 films can be effectively improved by adding moderate Mg2Sn phase and forming Mg3Bi2/Mg2Sn nanocomposite films.