High-performance thermoelectric properties of Cu2Se fabricated via cold sintering process

Abstract

The concept of a ‘phonon-liquid electron-crystal’ has received significant interest in recent years, with copper selenide (Cu2Se) emerging as one of the high-performance thermoelectric materials within this framework. This study focuses on the fabrication of Cu2Se bulk pellets through a low-temperature sintering method known as cold sintering process (CSP). The introduction of a liquid phase (thiol-amine solution) in this process facilitates the dissolution and precipitation of ion/atom clusters, resulting in sample densification. Remarkably, a sample density of nearly 90 % is achieved at a low sintering temperature of only 473 K. Furthermore, this CSP approach preserves the morphology of the Cu2Se precursor powders and effectively inhibits grain growth. Consequently, the lattice thermal conductivity of the CSP samples is significantly reduced, attributed to enhanced grain boundary phonon scattering. This leads to a substantial improvement in the figure-of-merit (ZT), increasing from 0.65 at 800 K in the hot-pressed sample to 2.13 at 800 K in the CSP sample. The advantages of CSP can be extended beyond Cu2Se, as it holds promise for enhancing the performance of various high-performance thermoelectric materials.