Power factor enhancement of -Zn₄Sb₃-InSb composites via arrays of p-n junction: Mixing p-type and n-type thermoelectric materials

The lead-free and abundantly available nature of beta-Zn4Sb3 makes it a promising thermoelectric material for mid-high temperature applications. We produce composites by embedding 1 wt %, 3 wt %, and 5 wt % of n-type InSb into the p-type beta-Zn4Sb3 host, enhancing both electrical conductivity and thermopower. At 600 K, the electrical resistivity decreases to 55 mu Omega-m from 71 mu Omega-m for the beta-Zn4Sb3 host. Surprisingly, the thermopower of the beta-Zn4Sb3/3 wt % InSb composite increases to 209 mu V/K from 180 mu V/K for the beta-Zn4Sb3 host, contrary to expectations. This enhancement can be attributed to p-n junctions between the p-type beta-Zn4Sb3 and n-type InSb. The power factor of the beta-Zn4Sb3/3 wt % InSb composite increased to 787 mu W/mK(2) from 452 mu W/mK(2) for the beta-Zn4Sb3 host. Despite higher thermal conductivity, the beta-Zn4Sb3/3 wt % InSb composite achieved the highest zT value of similar to 0.67 at around 600 K, 67.5 % higher than the beta-Zn4Sb3 host's zT value of 0.40.