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

Mg 3 Bi 2 /Mg 2 Sn nanocomposite films were prepared on single Si substrate using high pure metal Mg, Mg 3 Bi 2 and Mg 2 Sn target by alternately sputtering. The phase composition of the deposited Mg 3 Bi 2 /Mg 2 Sn films was analyzed by X-ray diffraction patterns. The surface and cross-sectional morphology of the deposited Mg 3 Bi 2 /Mg 2 Sn films was observed by scanning electron microscope. The content and distribution of elements in the deposited Mg 3 Bi 2 /Mg 2 Sn 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 Mg 3 Bi 2 /Mg 2 Sn films were composed of Mg 3 Bi 2 , Mg 2 Sn 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 Mg 2 Sn 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 mW·m −1 ·K −2 at 155 °C, and then decreased. The deposited Mg 3 Bi 2 /Mg 2 Sn nanocomposite films with 6.5 at.% Sn possessed the highest power factor in measured temperature range. The power factor of deposited Mg 3 Bi 2 films can be effectively improved by adding moderate Mg 2 Sn phase and forming Mg 3 Bi 2 /Mg 2 Sn nanocomposite films.