Crystallographic features and tetragonal phase stability of PbVO3, a new member of PbTiO3 family

Crystallographic features and stability of the tetragonal phase of PbVO3 were investigated under ambient and high pressure and compared with those of PbTiO3, PbVO3 is isotypic with PbTiO3 [at 300 K, space group P4mm; a = 3.803 91(5) Angstrom and c = 4.676 80(8) Angstrom, Z = 1]. Tetragonality (c/a) of PbVO3 was the largest among the PbTiO3-type compounds and increased monotonically with increasing temperature from 12 to 570 K without transition to cubic phase. The large tetragonality and the atomic position determined from synchrotron X-ray powder diffraction data suggest a large ferroelectric polarization above 100 muC/cm(2). Above 570 K in air, PbVO3 was oxidized to Pb2V2O7. Application of high pressure prevented the oxidation and thus a tetragonal-to-cubic phase transition accompanied by an insulator-to-metal phase transition was observed from about 2 GPa at room temperature.