Promising Thermoelectric Properties for Barium Pnictide Material

Thermoelectric materials are a critical tool in energy conservation because they are capable of regenerating electricity from thermal energy, i.e. from waste heat. The thermoelectric power of a material is quantified by the dimensionless thermoelectric figure of merit, ZT (ZT=S²T/ρκ).

The ideal thermoelectric material with maximized ZT will have low electrical resistivity ρ, low thermal conductivity κ, and high Seebeck coefficient S. However, designing a material which meets each of these conditions is non-trivial, as these parameters are interdependent. Because the thermoelectric power is proportional to the square of the Seebeck coefficient, one strategy to enhance ZT is to focus on enhancing the Seebeck, which can be achieved by lowering the carrier concentration in the material. Here, we report the thermoelectric properties of Ba₄AgGa₅As₈, a semiconducting bulk powder with a very high room-temperature Seebeck coefficient.

In its original report, Ba₄AgGa₅As₈ has been explored only in terms of its nonlinear optical potential. Here, we optimize the synthesis such that phase-pure powder is consistently obtained and study thermoelectric properies on sintered Ba₄AgGa₅As₈ pellets. Seebeck coefficient measurements on densified pellets reveal a high room-temperature Seebeck coefficient of 290 µV/K, which is expected to further increase with temperature. Coupled with its low thermal conductivity, Ba₄AgGa₅As₈ remains extremely promising for thermoelectric applications.