High Temperature XRD of Phase Transition in Piezoelectric PbNb2O6 across its Curie Temperature

Orthorhombic phase of lead metaniobate (PbNb2O6) is piezoelectric with a high Curie temperature (>570°C) with high potential of wide use in important high temperature applications that cannot be covered by the popular piezoelectric materials based on BT and PZT. Difficulty of preparing it in pure phase hindered full characterization and wide use of this long known piezoelectric material. Here, PbNb2O6 pellets have been prepared in pure orthorhombic phase and first characterized by room temperature TEM and XRD techniques, with a satisfying agreement of the two results. Next, we carried out high temperature x-ray diffraction study of its ferroelectric to paraelectric phase transition on heating across the Curie temperature, and also traced the cooling path. On heating the sample to 590°C and cooling back, there is a significant increase of cell volume.