Insulator-metal transition of highly compressed cerium sulfide*

We have studied room temperature electrical resistance and the Raman spectra of Ce₂S₃ up to pressures of 60 GPa as well as low temperature electrical resistance. Three phase transitions were observed at room temperature at 15 and 25 GPa based on changes in Raman spectra. The initial transitions are followed by and insulator to metal transition at 40 GPa, determined by a seven order of decrease in electrical resistance, the disappearance of Raman modes, and the change in appearance from opaque to reflective. The temperature dependence electrical resistance measurements support the conclusion that Ce₂S₃ is an insulator at low pressures and a metal above 40 GPa.