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

The pressure behavior of the absorption edge of PbWO4 was studied up to 15.3GPa. It redshifts at −71meV∕GPa below 6.1GPa, but at 6.3GPa the band gap collapses from 3.5to2.75eV. From 6.3to11.1GPa, the absorption edge moves with a pressure coefficient of −98meV∕GPa, undergoing additional changes at 12.2GPa. 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 and 12.2GPa are attributed to phase transitions.