Incorporation of aliovalent dopants into the bismuth-layered perovskite-like structure of BaBi4Ti4O15

The solid solubility of the aliovalent dopants Fe3+ and Nb5+ in the BaBi4Ti4O15 compound, a member of the family of Auri-villius bismuth-based layer-structure perovskites, has been studied using quantitative wavelength-dispersive spectroscopic microanalysis (SEM/EPMA) in combination with X-ray powder diffractometry (XRPD). The samples with nominal (starting) compositions corresponding to the chemical formulas BaBi4Ti4-4xFe4xO15 and BaBi4Ti4-4xNb4xO15 were prepared by hot forging a mixture of BaTiO3 and Bi4Ti3O12 with additions of Fe2O3 or Nb2O5 followed by a long annealing at 1100 degreesC. The study showed that an excess charge introduced into the structure by the substitution of Ti4+ ions with aliovalent dopants was preferentially compensated by a change in the ratio of Ba2+ to Bi3+ ions in the host structure according to the general formulas of the solid solutions Ba1-4xBi4+4xTi4-4xFe'O-4x(15) and Ba1+4xBi4-4xTi4-4xNb4xO15.