Fast, Simple, and Cost‐Effective Fabrication of High‐Performance Thermoelectric Ag2Se through Low‐Temperature Hot‐Pressing

Abstract

Silver selenide (Ag2Se) is a promising thermoelectric material for near‐room temperature applications. This study proposes a fast, simple, and cost‐effective method for producing high thermoelectric performance bulk Ag2Se. Ag2Se powders were synthesized from Ag and Se powders via a one‐hour wet ball milling process, followed by the fabrication of bulk pellets through low‐temperature hot‐pressing (130‐250 °C) with a mere 0.5‐hour holding time. Both Ag2Se powders and bulk pellets exhibited a single phase of orthorhombic β‐Ag2Se phase, with uniform compositional distribution Microstructural analysis revealed distinct grain boundaries in samples hot‐pressed below 190 °C, transitioning to grain coalescence was at 190 °C and 250 °C. The thermoelectric and transport measurements demonstrated that the electrical conductivity decreased and the Seebeck coefficient increased with hot‐pressing temperatures from 130 °C and 190 °C primarily due to reduced carrier concentrations. Thermal conductivity decreased with increasing hot‐pressing temperatures up to 190 °C, attributed to the weak chemical bonding of Ag2Se and the presence of defects. This resulted in a peak zT over 1.0 at 300 K, with an average zT close to 1.0 from 300 to 380 K. Despite lower temperatures and shorter processing times, the method produces Ag2Se with zT values comparable to more intricate techniques.