DIELECTRIC-PROPERTIES OF CERAMICS WITHIN THE BAO-LN2O3-TIO2 SYSTEM

The crystal structure of some inorganic compounds with general formula Ba6-xLn8+2x/3Ti18O54 - orthorhombic symmetry, sp. gr. Pba2, - satisfies the structural criteria for ferroelectricity. Ceramic materials corresponding to some particular compositions of this family have been prepared by solid state reaction and natural sintering at high temperature. Their low frequency dielectric characteristics have been studied between 300 and 800 K. For each composition, the dielectric constant shows a strongly pronounced maximum in the range 760-920 K depending on both the composition and the frequency. This dielectric behaviour should be related to a ferroelectric-paraelectric phase transition with a diffuse character.