From ferroelectric to relaxor behaviour in the Aurivillius-type Bi4−xBaxTi3−xNbxO12 (0≤x≤1.4) solid solutions

Solid solutions of the Aurivillius-type compounds with Bi4−xBaxTi3−xNbxO12 formula were prepared by solid-state reaction of the constitutive oxides at optimised temperatures. The room temperature structural data were obtained from X-ray diffraction (XRD). The solubility limit of (Ba, Nb) was estimated to x=1.4. The dielectric properties of sintered ceramics were investigated in wide temperature (25-800 °C) and frequency (1 kHz-1 MHz) ranges. For low substitution rates (0≤x≤0.4) the compounds behave as normal ferroelectrics with Curie temperature decreasing with increasing x. For x≥0.6, the materials exhibit a ferroelectric relaxor-type behaviour which was correlated to the relaxation of polar clusters induced by the heterovalent substitution on Bi and Ti sites.