The tetrahedrite Cu12Sb4S13 undergoes a metal-semiconductor transition (MST) at TMST = 85K, whose mechanism remains elusive. Our Cu 2p X-ray photoemission spectroscopy study revealed the monovalent state of Cu ions occupying the two sites in this compound. This fact excludes the possibilities of previously proposed antiferromagnetic order and Jahn-Teller instability inherent in a divalent Cu system. A synchrotron X-ray diffraction study has revealed that the body-centered cubic cell of Cu12Sb4S13 transforms into a body-centered 2a × 2a × 2c tetragonal supercell below TMST, where the cell volume per formula unit expands by 0.25%. We have further studied pressure effects on the MST as well as the effects of the substitution of As for Sb. The application of pressure above 1 GPa completely inhibits the MST and leads to a metallic state, suggesting that the low-Temperature structure with a larger volume becomes unstable under pressure. The As substitution also reduces the volume and suppresses the MST but the full substitution induces another transition at 124 K.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)