Crystal Structure Analysis and Phase Transition in Lead Orthovanadate Pb₃(VO₄)₂

Abstract

X-ray scattering experiments of lead orthovanadate, Pb 3 (VO 4 ) 2 , were carried out above and below the ferroelectric transition temperature T 2 =273 K, using a monodomain crystal. The space groups were confirmed to be C 5 2h – P 2 1 / c and C 3 2 – A 2 above and below T 2 , respectively. The structure analyses were conducted at several temperatures in both phases. The R-factors were less than 0.060 above T 2 and 0.045 below T 2 . The spontaneous polarizations were calculated from the atomic positions in the ferroelectric phase and compared with the values observed by the pyroelectric measurement by Midorikawa et al. The mechanism of the ferroelectric phase transition is discussed in terms of the mode of atomic displacements.