Microstructure and thermoelectric properties in Fe-doped ZrCoSb half-Heusler compounds

This study aimed to understand the effect of Fe-doped ZrCoSb-based half-Heusler compounds on the microstructures and thermoelectric properties. ZrFexCo1−xSb (x = 0-0.6) were prepared by arc melting. XRD results indicated that α-Fe, ZrCoSb half-Heusler phase and Fe0.63ZrSb can be found in ZrFexCo1−xSb alloy. In addition, the peak of Fe0.63ZrSb increase with increasing of Fe content. SEM results show a tendency of grain refinement, where the grain size decreases with increasing of Fe content. The Seebeck coefficient changed from negative to positive by Fe doping, and the electrical conductivity increased with increasing Fe content. The thermal conductivity for ZrFexCo1−xSb is considerably reduced, because the point defects, mass fluctuations and strain field effects induced by Fe substitution for Co intensively scatter the thermal phonons. Fe doping improved the thermoelectric figure of merit ZT of ZrFexCo1−xSb and the maximum ZT value of 0.036 was obtained for ZrFe0.2Co0.8Sb sample at 900 K.