Structure-property relationships in BaTiO3-BiFeO3-BiYbO3 ceramics

Ba1-xBixTi1-xYbx/2Fex/2O3 ceramics were fabricated by the solid state reaction method. X-ray diffraction analysis show 0 ≤ x ≤ 0.04 ceramics to have an average crystal structure described by the non-centrosymmetric tetragonal P4mm space group, whereas x ≥ 0.08 ceramics are consistent with a centrosymmetric cubic perovskite (space group Pm-3m). Coexistence of both tetragonal and cubic symmetries is observed for x=0.06. Raman spectroscopy analysis corroborate a change in average structure with increasing x, but also show the local crystal symmetry for x ≥ 0.08 ceramics to deviate from the idealized cubic perovskite structure. Dielectric data show a ferroelectric-to-relaxor crossover, which occurs in conjunction with the change in both the average and local crystal symmetry as indicated by X-ray and Raman data. For x ≥ 0.08, ceramics exhibit weak-relaxor behavior, which is also accompanied by a shift of the permittivity maxima towards higher temperatures with increasing x.