High-performance electron-doped GeMnTe2: hierarchical structure and low thermal conductivity

GeTe has attracted extensive interest due to its promising mid-temperature thermoelectric performance, yet the high cost and ferroelectric phase transformation may limit its application. Here, we explore the thermoelectric properties of electron doped GeMnTe2, which is a much cheaper derivative of GeTe with a rock-salt structure and a high thermoelectric figure of merit (ZT value) of 1.4. It is substantiated that an all-scale hierarchical structure including point defects at the atomic scale, endotaxially embedded nano-inclusions and precipitates are responsible for the strong scattering of phonons and low lattice thermal conductivity. Further synergistic modulation of electrical and thermal transport properties is successfully realized by Pb doping, which is effective in optimizing the carrier concentration and suppressing the phonon propagation by lattice softening and enhanced point defect scattering. The present work revealed the potential of GeMnTe2 as a promising candidate for mid-temperature thermoelectric materials and demonstrated the effectiveness of nanostructuring to enhance the thermoelectric performance.