Properties of lanthanide containing Aurivillius phases Ln2Bi3FeTi3O15 (Ln = La, Pr, Nd, Sm, Gd)

The phase formation in the series Ln2Bi3FeTi3O15 (Ln = La, Pr, Nd, Sm, Gd) was studied. It was found that the layered perovskite structure was formed after annealing at 1000 °C. Further increase in the synthesis temperature to 1100 °C did not affect the phase composition, excluding Gd-containing sample, where perovskite structure was partially destroyed to form the pyrochlore phase based on Bi2Ti2O7. Reversible anomalies obtained by differential thermal analysis indicate the phase transitions with a change in the crystal lattice symmetry in case of a perovskite-like phase and a transition of the order-disorder type in case of a pyrochlore structure.