Structural phase transitions in loparite-(Ce): evidences from Raman light scattering

• Published in: Journal of Raman spectroscopy Vol. 46; no. 1; pp. 161 - 166
• Main Authors: Popova, E. A., Yakovenchuk, V. N., Lushnikov, S. G., Krivovichev, S. V.
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.01.2015; Wiley Subscription Services, Inc
• Subjects: Anomalies; Ferroelectric materials; Ferroelectricity; ferroelectrics; Light scattering; mineral; optical phonons; Order disorder; Perovskites; Phase transformations; phase transition; Raman spectra
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.4587

Raman spectroscopic studies of loparite‐(Ce), a mineral of the perovskite family, are presented. Polarized Raman spectra were obtained in the temperature range of 50–300 K. As analysis of the behavior of Raman modes showed, the temperature dependences of wavenumber, damping and intensity of the optical modes exhibited anomalies near 220 and 150 K. Softening of the low‐wavenumber modes observed in the vicinity of 150 K is interpreted as an evidence of a ferroelectric phase transition. An anisotropic quasielastic light scattering in the low‐wavenumber region of the Raman spectra was observed from 300 to 150 K. As the data suggest, loparite‐(Ce) has two structural phase transitions, one of which (at 150 K) is a ferroelectric transition of the order–disorder type. Copyright © 2014 John Wiley & Sons, Ltd. Raman scattering studies of loparite‐(Ce), a mineral of the perovskite family, revealed anomalies in the temperature behaviors of optical modes. Analysis of the data suggests that structural phase transitions occurred at T = 220 and 150 K. It could be expected that the phase transition near 150 K was ferroelectric the first order. The existence of the relaxation mode in the low‐wavenumber region of the Raman spectra with the VV polarization indicates that the transition at 150 K is of the order–disorder type.