RELATIONSHIPS BETWEEN THE TEXTURE AND STRUCTURE OF BATIO3 AND ITS TETRAGONAL-]CUBIC TRANSITION ENTHALPY

A nanometric BaTiO3 powder sample with a medium crystallite size D = 1 57 Angstrom has been prepared from the thermal decomposition of BaTiO( C2O4). 4.5H(2)O by constant rate thermal analysis (CRTA), Rietveld ana lysis of the XRD pattern shows that this BaTiO3 sample presents a crys talline cubic structure, The evolution of the texture, the structure, and the ferroelectric --> paraelectric enthalphy transition as a funct ion of the annealing temperature of BaTiO3 has been followed from XRD and DSC experiments, A relationship has been found between the reactio n enthalphy of the tetragonal --> cubic polymorphic transition and the tetragonality of the sample, as measured from the c/a ratio, Therefor e, the calorimetric data can be used for predicting the structure of t his material, The Curie temperature seems to independent of the crysta llite size D, provided that it is higher than about 400 Angstrom. (C) 1996 Academic Press, Inc.