PHASE-TRANSITIONS AND DIELECTRIC-PROPERTIES IN SOME COMPOUNDS WITH BISMUTH OXIDE LAYER STRUCTURE

Solid solutions deriving from ferroelectric Bi3TiNbO9 by cationic substitutions of La3+ for Bi3+ and (Ti4+,W6+) for Nb5+ have been synthesized using a standard ceramic method. Evolutions of unit cell parameters and dielectric properties as a function of the substitution are given. All compounds show a ferroelectric phase transition, the temperature of which decreases with increasing substitution rate. The relations between the crystal chemical data and the dielectric behavior are discussed.