Phase Boundary Mapping of Tin-Doped ZnSb Reveals Thermodynamic Route to High Thermoelectric Efficiency

The thermoelectric material ZnSb utilizes elements that are inexpensive, abundant, and viable for mass production. While a high thermoelectric figure of merit zT, is difficult to achieve in Sn-doped ZnSb, it is shown that this obstacle is primarily due to shortcomings in reaching high enough carrier concentrations. Sn-doped samples prepared in different equilibrium phase spaces in the ternary Zn-Sb-Sn system are investigated using phase boundary mapping, and a range of achievable carrier concentrations is found in the doped samples. The sample with the highest zT in this study, which is obtained with a carrier concentration of 2 x 10(19) cm(-3) when the material is in equilibrium with Zn4Sb3 and Sn, confirms that the doping efficiency can be controlled by preparing the doped sample in a particular region of the thermodynamic phase diagram. Moreover, density functional theory calculations suggest that the doping efficiency is limited by the solubility of Sn in ZnSb, as opposed to compensation from native defects. Cognizance of thermodynamic conditions is therefore crucial for rationally tuning the carrier concentration, a quantity that is significant for many areas of semiconductor technologies.

Automated summary

The study reveals that controlling doping efficiency by preparing doped samples in specific regions can lead to high thermoelectric figure of merit zT in Sn-doped ZnSb. Calculations using density functional theory indicate that the doping efficiency is limited by the solubility of Sn in ZnSb.