A comprehensive review of entropy engineered GeTe: an antidote to phase transformation

Abstract

Driven by the burgeoning demand for high performance eco-friendly thermoelectric materials in the mid-temperature range (573–773 K), we herein focus on GeTe based alloys that exhibit a high thermoelectric figure-of-merit >2.0 owing to their promising band structure with a conversion efficiency of ∼13.3% for the segmented module and ∼14% for the single leg device. However, the drawback is the phase transition at ∼700 K, which is inevitable, and the irony is that practical application of thermoelectrics has no space for phase transition, as it can be detrimental owing to the unexpected change resulting in deterioration of the devices under operation, thus limiting their mass-market applications either as power generators or as refrigerators. Nevertheless, a comprehensive review is needed for finding ways to cease or abase the phase transformation in the operating temperature regime. In this regard, the most recently developed GeTe-based thermoelectric materials are reviewed coupled with the blooming paradigm, i.e., entropy engineering. The review article thus summarizes the concept of entropy engineering owing to its contribution to boosting thermoelectric performance by increasing the configurational entropy of the system and cites several case studies. Towards the end, future scope and directions were proposed to use entropy tailored GeTe based alloys for the development of high efficiency power generators.