Effective enhancement of thermoelectric and mechanical properties of germanium telluride via rhenium-doping

Abstract

GeTe as one of the most promising medium temperature thermoelectrics has progressed leaps and bounds in recent years, largely thanks to a combination of its unique electronic, thermal and structural properties. Despite its various advantages, a major factor standing in the way of wide commercial adoptions lies in its unreliable mechanical properties. This work reports Re doping as a strategy to drastically enhance the mechanical properties of GeTe, resulting in Vickers microhardness as high as 342.6 H_v in Ge_0.88Sb_0.10Re_0.02Te, which is more than double that of pristine GeTe (145 H_v). Ge_0.88Sb_0.10Re_0.02Te also exhibited a Young's modulus of 64.1 GPa, substantially higher than many other binary chalcogenide thermoelectrics. The significant enhancement of GeTe in mechanical properties is mainly related to the mechanism of precipitation hardening. In addition, we found that while the electronic properties were slightly compromised with Re doping, the lattice thermal conductivity was reduced due to point defects scattering brought about by Re atoms. Therefore, a high zT value (>1.6) at 600–800 K is achieved in Ge_0.88Sb_0.10Re_0.02Te. Furthermore, above 10% device efficiency can be expected for the operating temperature between 300–800 K. Such a solution to strengthen the mechanical properties of GeTe using Re doping is expected to play a major part in the push for full-scale GeTe-based thermoelectric devices.