Enhanced thermoelectric performance of MXene/GeTe through a facile freeze-drying method

Abstract

As a great promising lead-free mid-temperature thermoelectric material, Germanium telluride (GeTe) has attracted recently a great deal of attention. However, the high carrier concentration caused by Ge vacancies and thermal conductivity have been a bottleneck of its widespread use in thermoelectrics. The incorporation of nano-second phase has been considered a promising method to address the above issues. However, how to choose a suitable nano-second phase and achieve uniform dispersion in the matrix is still difficult. In this work, uniform dispersion of 2D material MXene in the GeTe was realized by a simple freeze-drying method, successfully tuning the electron and thermal transport properties of GeTe-based alloys synchronously. The results revealed that the carrier concentration of GeTe-based composite gradually decreased from ∼1021 to ∼1020 cm−3 with the participation of MXene. The lowest thermal conductivity can reach 2.19 W m−1 K−1 for GeTe composites with 1.5 vol% MXene at 700 K, which is ∼25.8% lower than that of pristine GeTe. Benefiting from the reduced carrier concentration and thermal conductivity, a maximum ZT value of 1.13 at 700 K is achieved for the composites with 1.5 vol% MXene, showing a 20.2% improvement compared with that of pristine GeTe (∼0.94). These results point out the potential value of MXene in enhancing the performance of GeTe-based thermoelectric materials.