Effects of high-pressure on the structural, vibrational, and electronic properties of monazite-type PbCrO4

TL;DR

This study investigates how high pressure affects the structure, vibrations, and electronic properties of PbCrO4, revealing two phase transitions, including potential metallization, through experimental techniques.

Contribution

It provides detailed experimental insights into pressure-induced phase transitions and electronic changes in PbCrO4, including structural, vibrational, and electronic property characterization.

Findings

Identification of two pressure-induced phase transitions.

Observation of band-gap collapse at the first transition.

Possible metallization of PbCrO4 at high pressure.

Abstract

We have performed an experimental study of the crystal structure, lattice-dynamics, and optical properties of PbCrO4 (the mineral crocoite) at ambient and high pressures. In particular, the crystal structure, Raman-active phonons, and electronic band-gap have been accurately determined. X-ray-diffraction, Raman, and optical-absorption experiments have allowed us also to completely characterize two pressure-induced structural phase transitions. The first transition is isostructural, maintaining the monoclinic symmetry of the crystal, and having important consequences in the physical properties; among other a band-gap collapse is induced. The second one involves an increase of the symmetry of the crystal, a volume collapse, and probably the metallization of PbCrO4. The results are discussed in comparison with related compounds and the effects of pressure in the electronic structure explained. Finally, the room-temperature equation of state of the low-pressure phases is also obtained.