Raman study of the structural phase transition in the ordered perovskite Pb₂MgWO₆

Abstract

Lead magnesium tungstate Pb2MgWO6 undergoes a structural phase transition at about 310 K. This phase transition has been characterized by Raman spectroscopy. The main features of the Raman spectra, collected between 173 and 523 K, are consistent with group theoretical predictions though unexpected weak and broad signals are observed in the high-temperature phase. From the comparison between these results and the structures previously determined, it is concluded that the phase transition has a behaviour intermediate between pure displacive and order-disorder.