Thermoelectric studies in β-Zn4Sb3-the complex interdependence between thermal stability, thermoelectric transport, and zinc content

beta-Zn4Sb3 is reported to have poor thermal stability and there is a wide scatter in the thermoelectric figure of merit (ZT) measured by different groups. Here, we show that both these issues are related to the zinc concentration. Specimens of beta-Zn4Sb3 having different carrier concentrations (n) have been prepared and thermoelectric property measurements carried out between room temperature and 525 K. The maximum ZT is found to vary between 0.4 and 0.85. The cause of the large variation in ZT is the strong dependence of the lattice thermal conductivity (kappa(L)) on n which make ZT sensitive to small changes in zinc concentrations. Based on analytical calculations, we show that by changing the zinc interstitial to the zinc lattice ratio, it is possible to achieve the experimental kappa(L) variation. Thermal cycling of the electrical conductivity (sigma) has been performed and phase identification after each cycling is carried out from power x-ray data. Different trends are observed in the specimens depending on n with accelerated degradation occurring only in a certain range of n (similar to 1.2-2.5 x 10(20) cm(-3)) corresponding to low zinc content in the matrix. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794816]