CALPHAD as a powerful technique for design and fabrication of thermoelectric materials

Abstract

Phase diagrams have always been used as a roadmap for materials research in terms of melting, casting, crystal growth, joining, solid-state reaction, heat treatment, phase transformation, and so on. CALPHAD (CALculation of PHAse Diagram) offers a theoretical instruction through a plausible simulation based on Gibbs energies, which could bypass some difficult experiments, extrapolate to a multicomponent-system or metastable region to get complete thermodynamic and kinetic properties, and improve the consistency and accuracy of the measured phase diagram. The present work takes thermoelectric materials as a paradigm, illustrating how to interpret and utilize phase diagrams as well as other thermodynamic information to design target materials, with the aid of multi-component CALPHAD-base databases and software. Two main aspects including phase design and microstructure modulation are delivered by the fundamentals of CALPHAD modeling and concrete examples of thermoelectric alloys. Opinions about the challenges and potentials of its applications in thermoelectric systems are also pointed out.