Pressure-Induced Valence Change and Semiconductor–Metal Transition in PbCrO3

Abstract

Pressure-induced valence change and semiconductor–metal transition were revealed in perovskite compound PbCrO3 by X-ray absorption spectroscopy (XAS) and resistance measurements, respectively. The Cr L2,3 edge XAS spectra indicate a charge disproportionation of Cr (3Cr4+ → 2Cr3+ + Cr6+) at ambient pressure, suggesting that the ambient-pressure phase of PbCrO3 has complex local structure and cannot be explained using the simple cubic perovskite structure (Pm-3m). Upon compression up to 4.2 GPa, Cr3+ and Cr6+ ions were converted to Cr4+ via charge transfer, associated with semiconductor–metal transition. The high-pressure metal phase is determined to be cubic perovskite structure (Pm-3m). Compared with the previous X-ray diffraction experiment, the large volume collapse (∼9.8% at 1.6 GPa) may be related to valence change and semiconductor–metal transition.