THERMAL AND DIELECTRIC-PROPERTIES OF A NEW FERROELECTRIC LABGEO5

Thermal and dielectric properties of LaBGeO5, a new ferroelectric with a stillwellite-type structure are investigated. The specific heat, C(p), shows one clear anomaly (DELTAS = 0.114 R) at 802.5 K. The basic thermodynamic parameters are determined on the basis of the Landau theory. However, an additional hump in C(p) was found in a different sample just above T(c). This dependence on samples is confirmed by the measurements of dielectric constants. The appearance of the new intermediate phase may be caused by some impurities or defects. The Rhodes-Wohlfarth plot suggests that the nature of the phase transitions is of the displacive-type.