Current Research and Future Prospective of Iron-Based Heusler Alloys as Thermoelectric Materials

In last two decades, Half Heusler (HH) alloys proved themselves as a potential candidate for thermoelectric devices. This is not only due to their structural capability for demonstrating and integrating various new concepts to enhance the thermoelectric figure of merit (ZT) but also high thermal stability which is advantageous for thermoelectric devices. However, most of the efficient HH alloys consist of expensive elements which resist their commercial application. This encouraged the development of highly efficient Fe-based Full Heusler (FH) alloys which have almost similar advantages of HH alloys along with the economical benefit. The main challenge in Fe-based FH as efficient thermoelectric as HH alloys is the reduction of lattice thermal conductivity and optimization of carrier concentration. This could be done through the use of concepts like bulk nanostructuring/bulk nanocomposite and more recently introduced Panoscopic approach or all scale hierarchical architecturing engineering and band structure engineering. In this review, we firstly discussed about the current progress on Fe-based FH alloys along with the challenges in enhancing the figure of merits. Herein, we also discussed various approaches adopted in bulk as well as nanostructured FH alloys to circumvent the interdependency of parameters in achieving higher ZT. It ends with discussion of the future trends for Fe-based FH thermoelectric materials for waste heat recovery. Through this review, we not only explain the probability of finding efficient thermoelectric in Fe-based FH alloys but also give a blueprint for enhancing ZT in many other thermoelectric materials.