Loparite-(Ce), a natural ferroelectric with the perovskite-type structure

Abstract

We report on the results of studies of dielectric properties of loparite-(Ce), a naturally occurring member of the perovskite-type family of materials, in the temperature range of 80–400 K. A strong frequency dispersion attributable to disorder and a dielectric anomaly have been observed in the vicinity of T = 157 K. The behavior of the inverse dielectric permittivity 1/ε′(T) has been found to be well described by the Curie–Weiss law with parameters C = 2.2 × 105 K−1 and Tm = 157 K. Studies of a dielectric hysteresis demonstrated the presence of ferroelectric loops below Tm ≈ 157 K, which points to the existence of a ferroelectric phase transition at Tm. The behaviors of spontaneous polarization, remanent polarization, and coercive field indicate that the ferroelectric phase transition is of the first-order type.

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

“…Indeed, anomalies in the dielectric permittivity of loparite‐(Ce) have been observed . The analysis of the dielectric response reported in showed that the temperature behavior of the inverse dielectric permittivity in the vicinity of 157 K obeys the Curie–Weiss law with the value of the Curie constant typical of ferroelectric phase transitions in perovskites. Hysteresis loops and behavior of the temperature dependence of spontaneous polarization given in the paper indicate that a ferroelectric state arises in loparite‐(Ce)–Се at Т < 157 K. The temperature behavior of conductivity and dielectric permittivity in the vicinity of 220 K confirm our hypothesis that there is a lattice instability near 220 K .…”

“…Significant changes in the phonon frequencies should also be reflected in the temperature dependence of the dielectric response through the Lyddane–Sach–Teller relation . Indeed, anomalies in the dielectric permittivity of loparite‐(Ce) have been observed . The analysis of the dielectric response reported in showed that the temperature behavior of the inverse dielectric permittivity in the vicinity of 157 K obeys the Curie–Weiss law with the value of the Curie constant typical of ferroelectric phase transitions in perovskites.…”