Relaxor properties of Ba-based layered perovskites

Ferroelectric materials with Bi-layered structure such as SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) are now intensively investigated in view of their applications in non-volatile computer memories and high-temperature piezoelectric transducers. When Sr is substituted with Ba, significant disorder is induced and material exhibits broadening of the phase transition. In this work, BaBi2Ta2O9 (BBT) and Ba2Bi2Nb2O9 (BBN) ceramics were sintered using mixed oxide route. Dielectric properties were investigated in the temperature range 20-600 degreesC at frequencies 25 Hz to 1 MHz. Strong dispersion of the dielectric permittivity is found indicating relaxor nature of the phase transition. It is shown that the dielectric relaxation in BBN ceramics is different from that of conventional relaxors such as PbMg1/3Nb2/3O3 (PMN). Fitting with Vogel-Fulcher relationship is used to evaluate parameters of the dielectric relaxation such as freezing temperature and attempt frequency. (C) 2001 Elsevier Science Ltd. All rights reserved.