Diffuse Ferroelectric Phase Transition and Relaxor Behaviors in Ba-Based Bismuth Layer-Structured Compounds and La-Substituted SrBi4Ti4O15.

The dielectric characteristics of BaBi₂Nb₂O₉, BaBi₄Ti₄O₁₅, BaBi₈Ti₇O₂₇, and La-substituted SrBi₄Ti₄O₄ were investigated to discuss their ferroelectric phase transition and relaxor behaviors. BaBi₂Nb₂O₉ showed typical relaxor behaviors, and a shift of T_m with increasing frequency was observed in BaBi₄Ti₄O₁₅ and SrBi_{4− x}La _xTi₄O₁₅ ( x=0.8, 1.0) but they underwent a real paraelectric–ferroelectric phase transition on zero-field cooling, while BaBi₈Ti₇O₂₇ showed a normal ferroelectric nature. The reduced concentration and weakened coupling of the dipoles related to A-site bismuth are believed to be responsible for the appearance of short-range electric ordering and the relaxor behaviors in these bismuth layer-structured compounds. [ABSTRACT FROM AUTHOR]