Chemical pressure effect on thermoelectric properties of Ca and Ba substituted SrSi_2 alloys

摘要

We report the study of temperature-dependent electrical resistivity, Seebeck coefficient, and thermal conductivity of the Sr_(1-x)Ca_xSi_2 and Sr_(1-x)Ba_xSi_2 alloys to elucidate the chemical pressure effect on the thermoelectric performance, characterized by the figure-of-merit, ZT. It is found that the room-temperature electrical resistivity and thermal conductivity are slightly reduced through the substitution of Ca and Ba (x < 0.10) onto the Sr sites of SrSi_2. Moreover, the room-temperature Seebeck coefficients of these samples are substantially enhanced upon substitution. These promising results lead to a significant enhancement in the ZT value of the substituted SrSi_2 alloys as compared to the parent compound SrSi_2. Namely, the highest room-temperature ZT values of ～0.17 and ～0.11 were obtained for the Sr_(0.92)Ca_(0.08)Si_2 and Sr_(0.93)Ba_(0.07)Si_2 alloys, much larger than that of pure SrSi_2.