FERROELECTRIC AND MAGNETIC PROPERTIES OF PEROVSKITE STRUCTURED Bi1-x-yGdxBayFe1-yTiyO3 MAGNETOELECTRIC CERAMICS
Ternary solid solutions of BiFeO3 , GdFeO3 and BaTiO3 have been prepared by solid-state reaction method. Dielectric properties of these ceramics have been characterized in the temperature range between room temperature and 673 K and magnetic properties between 5 K and 300 K. For the understanding of the multiferroic property, the relation between the crystal structures, magnetic transition and ferroelectric transitions with increasing temperature have been analyzed. All ceramic samples show single perovskite phase. When Ba content exceeds 0.2 wt%, the sintering ability is weakened and the phase structure of Bi 1-x-y Gd x Ba y Fe 1-y Ti y O 3 (with x = 0.2 and y = 0.1, 0.2, 0.3, 0.4, 0.5) solid solution changes from rhombohedral to tetragonal phase. The maximum ferroelectric transition temperature (Te of this system was in the range 154–165°C with the dielectric constant peak of 6000 for y = 0.5 at 100 kHz. Well-saturated piezoresponse hysteresis loops were observed for all compositions indicating room temperature ferroelectricity. With increasing Ba content (up to 0.3 wt%) the remanent magnetization Mr increased and the coercive magnetic field decreased.