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=4n=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)Å, b=5.443(3)Å and c=41.77(2)Å. 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 Ea=0.017±0.002eV and freezing temperature TVF=558±1K. Relaxor behavior and the incidence of ferroelectric hystersis (PP vs EE) loop at room temperature suggested the coexistence of long-range polar ordering with the polar nanoregions induced by compositional fluctuations.