Abstract: Thermoelectric materials can directly convert thermal energy into electrical energy, offering significant potential for waste heat recovery applications. Ag₂Se as a novel low-temperature thermoelectric material has attracted considerable attention due to its unique crystal structure and excellent electronic transport properties. In this study, micro-sized Ag₂Se powders were synthesized via solvothermal method, which contributes to precise control over the powders’ structure, composition, and grain size. The results indicate that the synthesized Ag₂Se powders exhibit uniform micro-columnar structure with complete crystal lattice, and the Ag-to-Se ratio is close to the theoretical value (approximately 2 : 1 (in atom)). Furthermore, spark plasma sintering (SPS) was employed to densify the Ag₂Se powders at various temperatures, and the findings reveal that the sintering temperature has a significant impact on the microstructure and thermoelectric performance. The fracture surface of the sample sintered at 473 K is relatively dense, whereas samples sintered at 573 and 673 K display the emergence of nanopores. Notably, the nanopores are particularly pronounced in the sample sintered at 673 K, which effectively reduces the material’s lattice thermal conductivity (κ_l) to 0.14 W·m⁻¹·K⁻¹ at room temperature. Ultimately, the Ag₂Se bulk prepared under a sintering temperature of 573 K exhibited the best thermoelectric performance, achieving a room-temperature thermoelectric figure of merit (ZT) of 0.50. This study not only demonstrates the feasibility of the solvothermal method for fabricating high-performance micro-sized thermoelectric powders but also provides valuable experimental evidence for further optimizing the microstructure and thermoelectric properties of Ag₂Se materials.

Key words: Ag₂Se, thermoelectric property, solvothermal method, spark plasma sintering