Substitution mechanism and structural study of MnO-doped Bi2VO5.5-δ

The Aurivillius-type Bi2VO5.5-δ series doped by magnetic cations may have a significant electronic contribution to their total conductivity and special magnetoelectric properties which extend potential applications to magnetoelectronic and spintronic fields. Bi2(V1-xMnx)O5.5-δ and (Bi2-xMnx)VO5.5-δ (x = 0.10–0.30) compounds with nominal composition doped by manganese cation on the Bi- or V-site were prepared via a solid-state reaction. Results show that partial substitution of Mn on the V-site stabilizes Bi2(V1-xMnx)O5.5-δ in the high-temperature tetragonal structure of Bi2VO5.5-δ for compositions in the range 0.10 ≤ x < 0.25. The geometric magnetic frustration was observed through magnetic susceptibility analysis. The crystal structure was refined by the Rietveld method based on a four-oxygen-site model. The resulting solid-solution limit confirms the equatorial vacancy model which assumes that all vacancies are located on the equatorial oxygen sites. The possible substitution mechanism is determined which supports V ↔ Mn, rather than Bi ↔ Mn in the MnO-doped Bi2VO5.5-δ series.

► The possible substitution mechanism is determined which supports V ↔ Mn, rather than Bi ↔ Mn in the MnO-doped Bi2VO5.5-δ.
► The solid-solution limit (0.10 ≤ x < 0.25) accords with the Equatorial vacancy (EV) model.
► Mn2+/Mn3+ mixed valence is confirmed in the Bi2(V1-xMnx)O5.5-δ compounds.
► The refined crystal structure via a Rietveld method behaves four-oxygen sites.
► The refinement fit is good with Rp = 4.25%, χ2 = 7.82 (x = 0.10) and Rp = 4.82%, χ2 = 8.98 (x = 0.20).