Evaluating the phase transformations and cationic liquid-like behavior in tetragonal Cu2-xMnxS prepared under high pressure using high-resol

Among thermoelectric materials, Cu2-δS alloys display unique advantages of nontoxicity, a rather low cost, and environmental friendliness, and thus have aroused extensive research interest. Monoclinic γ-chalcocite, Cu2S, presents a rigid Cu-sublattice, while the β-hexagonal and α-cubic higher temperature phases have shown liquid-like ionic conductivity with excellent thermoelectric properties. Besides, the tetragonal δ-phase is formed under high pressure and has been proposed as a more stable structure for applications, but its investigation is still limited. The goal of this proposal is twofold: i) to characterize the structural features of the tetragonal phase at RT for a Cu2-xMnxS series prepared under high pressure; ii) to analyze the evolution across the phase transitions at low and intermediate temperatures (in the 200 - 750 K interval) of the tetragonal δ-phase Cu2S and of the Mn-doped derivatives, to use investigate the electronic density and the ionic disorder.