Thermoelectric performance of Mg2−xCaxSi compounds

Thermoelectric materials Mg2−xCaxSi (x = 0, 0.01, 0.03, 0.05, 0.07, 0.1) compounds have been prepared by vacuum melting followed by hot-pressing. Effects of the substitution of Ca for Mg on phase structures and the thermoelectric properties of the hot-pressed compounds were investigated. It was found that the alloying of Ca in Mg2Si based compounds increases the electrical conductivity and decreases the Seebeck coefficient of the compounds, due to the electronegativity difference between Ca and Mg. The dimensionless figures of merit of Mg2Si and Mg1.99Ca0.01Si reach, respectively, 0.41 and 0.34 at 660 K.