A Raman study of the low temperature phase transition of lead orthovanadate

Abstract

A Raman study of Pb3(VO4)2 crystal has been carried out in the 292 to 80 K range. The Raman spectra show manifestations of the ferroelectric phase transition, with Tc = 240 K, though no soft mode is detected. An anomalous shift of 9 cm-1 near Tc is recorded for the 822 cm-1 line which is assigned as a correlation-field split component of the v1(A1) fundamental of the vanadate ion. This indicates that as the crystal passes through Tc, the vanadate ion is strongly affected by the displacement of the lead atoms from the pseudo three-fold axis of the paraelectric D5 3d trigonal phase. The ferroelectric phase transition exhibits a thermal hysteresis of 30 K. © 1988.