Neutron diffraction study of B-site disordered Bi0.5Ca0.5Fe0.5Mn0.5O3

A polycrystalline sample of Bi 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 3 was synthesized via conventional solid-state reaction and structurally characterized using X-ray and neutron powder diffraction. To evaluate the possible presence of Fe/Mn ordering, Rietveld refinement of the neutron diffraction data was carried out using both the Pnma and P 2 1 / n structural models, leveraging the strong contrast in neutron scattering lengths between Fe and Mn. The analysis revealed no evidence of rock-salt–type B -site ordering typically observed in double perovskites. Refinement of the oxygen site occupancies confirmed the absence of oxygen vacancies, consistent with full stoichiometry. Furthermore, the regular geometry of the ⟨Fe/Mn⟩O 6 octahedra, indicated by uniform Fe/Mn–O bond lengths, supports the assignment of Fe 3+ and Mn 4+ oxidation states for the transition metals. This study provides further structural insight into Bi-based disordered double perovskites and underscores the utility of combined X-ray and neutron diffraction techniques for probing cation distributions in complex oxide systems.