FERROELECTRIC PHASE-TRANSITION IN LABSIO5 CRYSTALS FROM RESULTS OF THERMAL AND DIELECTRIC MEASUREMENTS

The specific heat of the ceramic and the permittivity of a single-crys tal sample of LaBSiO5, a new ferroelectric in the stilwellite family, were measured in a temperature range which includes the phase transiti on point (T-C = 140 degrees C). The excess entropy of the phase transi tion Delta S = 1.05 J/mol.K and the Curie-Weiss constant CC-W= 3.2 x 1 0(3) K were determined. The results indicate that the phase transition in this crystal is of a ''mixed'' nature and exhibits features of a d isplacement-type transition and an order-disorder transition. (C) 1998 American Institute of Physics.