Thermoelectric performance of lead-free manganese telluride via alkaline Mg doping for mid-temperature application

Abstract

Manganese telluride (MnTe) is a potential p- type semiconducting thermoelectric material in the mid temperature range. Herein, magnesium (Mg) is incorporated with Manganese telluride (MnTe) in the stoichiometric ratio of Mn1.12−xMgxTe (x = 0, 0.025, 0.05, 0.075, 0.1) via vacuum sealing and hot press densification methods. The interstitial Mn atoms and Mg atoms create point defects and mass fluctuation, simultaneously. Stacking faults, twin boundaries and lattice dislocations are distinguished from HRTEM (High resolution transmission electron microscope). These defects are acting as a phonon scattering centers results in reduced total thermal conductivity of 0.827 W/mK at 653 K for Mn1.02Mg0.1Te. The excess Mn atoms in MnTe matrix and the substituted Mg atoms firmly contribute to improve the electrical conductivity by producing more acceptor levels, which significantly enhance the power factor of 439 µW/mK2 at 753 K for Mn1.07Mg0.05Te. Consequently, the maximum zT of 0.33 is achieved at 803 K for Mn1.07Mg0.05Te due to the synergistic effects of increased electrical property and reduced thermal conductivity.