Multiple phase formation and its influence on lattice thermal conductivity in β-Zn4Sb3

The extremely low thermal conductivity (kappa) coupled with suitable Seebeck (S) and electrical conductivity (sigma) values makes beta-Zn4Sb3 a promising candidate for intermediate temperature (200-400 degrees C) thermogenerator applications. However, the poor thermal stability makes it difficult to reproduce the high thermoelectric figure of merit originally reported for this material.(1) Using a combination of surface scanning techniques (Potential Seebeck microprobe, electron backscatter diffraction, and x-ray diffraction), we investigate specimens of beta-Zn4Sb3 prepared under different synthesis conditions. Our results indicate the presence of multiple phases of Zn4Sb3 with distinct room temperature S values ranging from 70 to 140 mu V/K. Though crystallographically similar, these phases have very different lattice contribution to the thermal conductivity (kappa(L)), which vary between 0.45 and 1.0 W/mK and might predominantly reflect the degree of Zn disorder among the different phases.