Crystallographic Features and Tetragonal Phase Stability of PbVO3, a New Member of PbTiO3 Family

Crystallographic features and stability of the tetragonal phase of PbVO 3 were investigated under ambient and high pressure and compared with those of PbTiO 3 . PbVO 3 is isotypic with PbTiO 3 [at 300 K, space group P 4 mm; a = 3.803 91(5) Å and c = 4.676 80(8) Å, Z = 1]. Tetragonality ( c / a ) of PbVO 3 was the largest among the PbTiO 3 -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 μC/cm 2 . Above 570 K in air, PbVO 3 was oxidized to Pb 2 V 2 O 7 . 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.