Influence of thermal conductivity and of non-constant relaxation time on thermoelectricity in Mg3Sb2

We discuss the effects of different approximations to thermal conductivity and relaxation time on the thermoelectric figure of merit ZT in n-doped Mg3Sb2. We use density-functional electronic structure and Bloch-Boltzmann transport theory with an energy-dependent relaxation time. ZT is monotonically increasing with T in our range (300-700 K) with a maximum value of similar to 1.5.