Fe3+/Nb5+ co-doping effects on the properties of Aurivillius Bi4Ti3O12 ceramics

Bi4Ti3-x(Nb0.5Fe0.5)xO(12) (BTFNx) ceramics with 0 <= x <= 2 were synthesized to evaluate the effect of Fe3+/Nb5+ co-substitution into the B-site of Bi4Ti3O12 (BIT). We show that the XRD pattern for the compounds with x <= 1 is the characteristic one of a layered perovskite structure belonging to the n = 3 member of the Aurivillius family. Impurity peaks assigned to a pyrochlore phase are detected at higher concentrations. Raman measurements corroborated that Fe3+ and Nb5+ ions are incorporated into the Ti sites of the Aurivillius compound. Frequency dependent dielectric studies at room-temperature displayed the reduction of both dielectric constant and loss tangent with substitution, while the electric-field-induced polarization switching behavior indicates ferroelectric character. It is observed that the ferroelectric transition temperature decreases with increasing Fe/Nb content. Magnetic measurements indicated no evidence of ferromagnetic ordering, but antiferromagnetic spin correlations between Fe3+ ions. (C) 2017 Elsevier B.V. All rights reserved.