Effects of high pressure on the optical absorption spectrum of scintillating PbWO4 crystals

TL;DR

This study investigates how high pressure affects the optical absorption spectrum of PbWO4 crystals, revealing a band-gap collapse and phase transitions up to 15.3 GPa.

Contribution

It provides detailed insights into pressure-induced electronic and structural changes in PbWO4, including phase transitions and band-gap behavior.

Findings

Band-gap red-shifts at -71 meV/GPa below 6.1 GPa

Collapse of band-gap from 3.5 eV to 2.75 eV at 6.3 GPa

Additional changes in absorption edge at 12.2 GPa

Abstract

The pressure behavior of the absorption edge of PbWO4 was studied up to 15.3 GPa. It red-shifts at -71 meV/GPa below 6.1 GPa, but at 6.3 GPa the band-gap collapses from 3.5 eV to 2.75 eV. From 6.3 GPa to 11.1 GPa, the absorption edge moves with a pressure coefficient of -98 meV/GPa, undergoing additional changes at 12.2 GPa. The results are discussed in terms of the electronic structure of PbWO4 which attribute the behavior of the band-gap to changes in the local atomic structure. The changes observed at 6.3 GPa and 12.2 GPa are attributed to phase transitions.