Bismuth-free Mg3Sb2 with enhanced room-temperature thermoelectric and mechanical properties

Thermoelectric materials are competitive candidates for special cooling applications. Mg3Sb2-based materials consisting of inexpensive ingredients have profound thermoelectric properties. At present, alloying with Mg3Bi2 is the most effective approach to optimize the thermoelectric properties of Mg3Sb2-based materials. However, the extremely low abundance of bismuth in the crust contradicts its economic expectation. In this work, the ZrO2 micro-particles were separated into the Mg3.2Sb1.99Te0.01. The doping effect of Zr atoms at Mg sites increased the electrical conductivity, and the combined secondary phase lowered the lattice thermal conductivity. With acceptable degradation in the Seebeck coefficient, the sample combined with 5 % (in mass) ZrO2 exhibited a dimensionless figure of merit (zT) of 0.49 and a power factor of 2.7 mW·m−1·K−2 near room temperature. The average zT in the range from 300 K to 500 K reached 0.8, on par with the Mg3Sb2Mg3Bi2 alloys. Besides, the compressive and bending strengths reach 669 MPa and 269 MPa, respectively, far superior to the common room-temperature thermoelectrics. This secondary phase showed a surprising and uncostly promotion of the Mg3Sb2-based thermoelectric materials, impelling the realization of its commercial application.