Combinatorial Approach Based on Interdiffusion Experiments for the Design of Thermoelectrics: Application to the Mg₂(Si,Sn) Alloys

Thermoelectric materials are ranked by their ability to meet a criterion of excellence that is related to their conversion efficiency. This dimensionless figure of merit, zT = (σS2T)/κ, measures how well a candidate material can convert heat to electricity where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. This antagonist combination of properties controlling the performance of thermoelectrics makes it difficult to design these materials. Notwithstanding, it has been established that functional properties are controlled by both composition and microstructural parameters and that refined microstructures promote better thermoelectric properties.(1) This has led to new approaches inspired by metallurgical concepts that rely on the use of thermal treatments to generate and control microstructures that give the desired transport properties.(1-5) The combination of alloy composition and time and temperature that can be applied in a thermal treatment is nearly infinite; thus, identification of the optimal composition and treatment is very time-consuming using one-composition-at-a-time synthesis and property testing. Designers need the knowledge of thermodynamics and kinetics, as well as an understanding of the composition-microstructure-property relationships to better identify the most promising materials...