Relaxor behavior of BaBi4Ti3Fe0.5Nb0.5O15 ceramics

Monophasic BaBi4Ti3Fe0.5Nb0.5O15 (BBTFN) which exhibited relaxor ferroelectric properties has been synthesized via the solid-state reaction route. X-ray powder diffraction (XRD) studies carried out at room temperature confirmed the phase to be an n = 4 member of the Aurivillius family of oxides. The XRD pattern was indexed to an orthorhombic cell associated with lattice parameters a = 5.463(3) angstrom, b = 5.443(3) angstrom and c = 41.77(2) angstrom. A broad dielectric peak associated with the frequency dependent dielectric maximum temperature was observed. The high temperature slope of the dielectric peak was characterized by the Lorenz-type quadratic law for relaxors. The dielectric relaxation was modeled using the Vogel-Fulcher relationship with activation energy E-a = 0.017 +/- 0.002 eV and freezing temperature T-VF = 558 +/- 1 K. Relaxor behavior and the incidence of ferroelectric hystersis (P vs E) loop at room temperature suggested the coexistence of long-range polar ordering with the polar nanoregions induced by compositional fluctuations. (C) 2008 Elsevier Ltd. All rights reserved.