Dielectric response of ceramic Sr2−xBixTi2−xFexO6 (0≤x≤1.5) perovskites

Polycrystalline Sr2−xBixTi2−xFexO6 (x=0, 0.5, 1 and 1.5) perovskites have been synthesized by the ceramic method. Structural characterization from X-ray diffraction data showed that the symmetry evolves from centrosymmetric cubic (Pm3¯m) to non centrosymmetyric rhombohedral (R3c) as iron and bismuth content increase. For the intermediate composition, x=1, a mixed phase is obtained, which mean symmetry matches the best with the orthorhombic one (Pbnm). EDS analyses showed that the effective compositions differ from the nominal ones, and they were confirmed from Rietveld refinements of XRD data. HRTEM experiments indicated that in the case of x=1.5, a superstructure along [001]c and [111]c is observed. The dielectric response is modified depending on the composition range x. The x=0 compound shows a Debye type relaxation implying oxygen vacancy cluster, whereas a relaxor ferroelectric behavior is obtained for the x=0.5 and x=1 samples. Finally, in the case of x=1.5, the dielectric behaviour is characterized by strong dependence of permittivity with temperature. [Display omitted] •Powdered samples of the Sr2−xBixTi2−xFexO6 (x=0, 0.5, 1 and 1.5) perovskites have been synthesized by the ceramic method, leading to microsized cystals.•Powder XRD data revealed a change in symmetry from cubic to rhombohedral as x increases.•The structural changes were confirmed by EDS and HRTEM analyses and are correlated with the observed changes in the dielectric response of the materials.