Deciphering Silver Diffusion Pathway and Local Structure of Thermoelectric Ag ₈ SnSe ₆

Abstract Argyrodite compounds have garnered significant attention for their exceptional thermoelectric (TE) properties, with Ag 8 SnSe 6 standing out as a prominent high‐performance material, particularly at elevated temperatures. Ag 8 SnSe 6 undergoes an order–disorder phase transition, which leads to the formation of a 3D percolation network of Ag ion transport in the disordered high‐temperature phase. Despite significant interest in the TE properties of Ag 8 SnSe 6 , systematic experimental studies on its crystal structures, particularly the local structure in the disordered and ordered states and Ag ion migration pathways, remained largely unexplored. This study focuses on the structural evolution during phase transition and Ag ion diffusion at elevated temperatures. Synchrotron X‐ray total scattering is utilized to systematically study the crystal structure and local atomic environment, especially across the phase transition. Additionally, synchrotron single‐crystal X‐ray diffraction is combined with the maximum entropy method (MEM) to provide a detailed analysis of the Ag ion migration pathways. The findings clarify the specific Ag diffusion channels connecting different Ag ions in Ag 8 SnSe 6 , offering valuable structural insights that serve as a benchmark for understanding the TE properties.