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

Pressure-induced valence change and semiconductormetal transition were revealed in perovskite compound PbCrO3 by X-ray absorption spectroscopy (XAS) and resistance measurements, respectively. The Cr L-2,L-3 edge XAS spectra indicate a charge disproportionation of Cr (3Cr(4+) -> 2Cr(3+) + 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 C-r6+ ions were converted to Cr4+ via charge transfer, associated with semiconductormetal 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 (similar to 9.8% at 1.6 GPa) may be related to valence change and semiconductormetal transition.