Crystallographic phases in PbNb2O6 and Piezoelectricity

Abstract Emerging high temperature (HT) applications of piezoelectric (PE) materials in areas like nuclear Fast Breeder Reactors and rocket exhausts need PE materials with high Curie temperature. For decades, the rhombohedral (r) phase, stable form of lead metaniobate (PbNb2O6) has been assigned the space group R3m, and found non-piezoelectric. So, its study has been ignored in favour of the metastable orthorhombic PbNb2O6, showing T(Curie) > 570°C and serving HT PE applications. Our new findings on r-PbNb2O6 from DSC-TGA, impedance spectroscopy and x-ray Rietveld analysis, probe recent claims of polar R3 space group and hints of its ferroelectric phase up to ∼815°C.