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 t hermodynamic parameters are determined on the basis of the Landau theo ry. However, an additional hump in C(p) was found in a different sampl e just above T(c). This dependence on samples is confirmed by the meas urements of dielectric constants. The appearance of the new intermedia te phase may be caused by some impurities or defects. The Rhodes-Wohlf arth plot suggests that the nature of the phase transitions is of the displacive-type.