Polarization Properties of Superlattice-Structured Bi4Ti3O12-BaBi4Ti4O15 Single Crystals and Ceramics: Comparison with Bi4Ti3O12 and BaBi4Ti4O15

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Superlattice-structured Bi4Ti3O12-BaBi4Ti4O15 (BiT-BBTi) ceramics and single crystals were prepared, and their crystal structure and polarization properties were compared with those of constituent BiT and BBTi. The Curie temperature ($T_{\text{C}}$) of the BiT-BBTi crystals was 540°C, which was 40°C higher than that of the BiT-BBTi ceramics with the stoichiometric composition. The BiT-BBTi ceramics had a remanent polarization ($P_{\text{r}}$) of 12 μC/cm2, while the spontaneous polarization ($P_{\text{s}}$) along the $\mathbf{a}$ axis of the BiT-BBTi crystals was 52 μC/cm2, which was larger than those of BiT and BBTi crystals. The large $P_{\text{s}}$ observed for the BiT-BBTi crystals is suggested to originate from the ferroelectric displacements of the Bi of Bi2O2 layers as well as from the Bi substitution for Ba induced by compositional deviation.
2004-09-15