In-situ high-pressure Raman scattering studies in PbWO4 up to 48 GPa
Résumé
The effect of pressure on the Raman spectrum of PbWO4 has been investigated up to 48 GPa in a
diamond-anvil cell using neon as pressure-transmitting medium. Changes are detected in the Raman
spectrum at 6.8 GPa as a consequence of a structural phase transition from the tetragonal scheelite
structure to the monoclinic PbWO4-III structure. Additional changes are detected in the Raman spectra at
15.5 and 21.2 GPa. They are proposed to be the consequence of two additional phase transitions to the
previously unknown crystalline phases IV and V. Additionally, at 47.7 GPa all Raman modes disappear,
which could be caused by a pressure-induced amorphization. All structural changes are reversible, being
the scheelite phase recovered at ambient pressure. However, the two most intense modes of the PbWO4-
III phase are still present after full decompression, indicating that this phase coexists as a minority
metastable phase with the scheelite phase after pressure release. The wavenumber of the Raman modes
and their pressure dependencies are reported for the four crystalline phases. The present reported results
are compared with previous studies.