Ultra-low lattice thermal conductivity of MgPb$_2$Te -- A first\n principles study

Thermoelectric technology is an alternate way to efficiently utilize the\nenergy by converting waste heat into electricity. Thermoelectric requires\nmaterial with low thermal conductivity to improves its thermoelectric\nperformance. In this work, by solving Boltzmann transport equation based on\nfirst principles calculations, we report an ultra-low room temperature thermal\nconductivity of 2.08 Wm$^{-1}$K$^{-1}$ and 2.9 Wm$^{-1}$K$^{-1}$ along c-axis\nand a-axis respectively for pure MgPb$_2$Te. To explain this ultra-low thermal\nconductivity, we analyzed the elastic constants, phonon group velocity,\nphonon-phonon scattering and contribution from transverse acoustic,\nlongitudinal acoustic and optical phonon branches. We also report the thermal\nconductivity of MgPb$_2$Te nanostructures. At 50 nm, the room temperature\nthermal conductivity of MgPb$_2$Te is 0.957 Wm$^{-1}$K$^{-1}$ and 1.459\nWm$^{-1}$K$^{-1}$ along c-axis and a-axis respectively. Ultra-low thermal\nconductivity unraveled in this work shows MgPb$_2$Te would a promising material\nfor thermoelectric applications.\n