New insights into the effect of chemical bonding strength on thermoelectric performance and stability in YbMg2Bi2 toward practical thermoelectric applications

It is currently widely accepted that chemical bonding in a thermoelectric material should be weakened as much as possible to obtain a lower lattice thermal conductivity and thus a higher thermoelectric figure of merit, zT, but the consequent reliability issues, such as inferior structural stability and mechanical brittleness, are rarely emphasized. Here, experimental studies on p-type YbMg2Bi2-based compounds demonstrate the advantageous effects of chemical bonding stiffening toward practical applications. Despite the stronger chemical bonding in Sb-alloyed YbMg2Bi2, the compound still exhibits lower lattice thermal conductivity than its parent YbMg2Bi2 compound, as well as a comparable average zT, due to rigorous point defect scattering. More importantly, chemical bonding toughening guarantees better maintenance of thermoelectric performance under high temperatures and improved mechanical properties, both of which are essential for the durable operation of thermoelectric generators. This research provides a new way of thinking about chemical bonding engineering toward practical thermoelectric applications.