Effect of La-substitution on the structure and dielectric properties of BaBi4Ti4O15 ceramics

Four-layer Aurivillius compound BaBi4-xLaxTi4O15 (x = 0.1-1.0) is synthesized by a modified chemical route. X-ray diffraction analysis confirms the formation of single-phase Aurivillius compound. The crystal structure of compound changes from orthorhombic to pseudo-tetragonal at x = 0.5. BaBi4-xLaxTi4O15 shows typical relaxor behaviour. With increasing La3+ substitution, shift of Tm towards lower temperature and increased relaxor behaviour is observed. The substitution also results in a marked improvement in the remnant polarization and coercive field. The Cole-Cole plots show the presence of two semicircular arcs, suggesting the existence of grain and grain-boundary effects. The dc-conductivity and activation energies for both grain and grain boundary are evaluated. The ceramics with x = 0.3 presents the lowest conductivity among all compositions.