Atomistic simulation and XAS investigation of Mn induced defects in Bi12TiO20

• Pure and Mn-doped Bi12TiO20 samples were studied by experimental techniques combined with atomistic simulation.
• Good agreement between experimental and simulation results was obtained.
• XANES results suggest a mixture of 3+ and 4+ valences for Mn, occupying the Ti4+ site in both cases.
• Charge compensation by holes is most energetically favoured, explaining the enhancement observed in AC dark conductivity.

This work reports an investigation of the valence and site occupancy of Mn dopants in Bi12TiO20 (BTO: Mn) host using X-ray Absorption (XAS) and atomistic simulation techniques based on energy minimisation. X-ray Absorption Near Edge Structure (XANES) at the Mn K-edges gave typical results for Mn ions with mixed valences of 3+ and 4+. Extended X-ray Absorption Fine Structure (EXAFS) results indicated that Mn ions are probably substituted at Ti sites. Atomistic simulation was performed assuming the incorporation of Mn2+, Mn3+ and Mn4+ ions at either Bi3+ or Ti4+ sites, and the results were compared to XANES and EXAFS measurements. Electrical conductivity for pure and doped samples was used to evaluate the consistency of the proposed model.

The structure of Bi12TiO20 (BTO).Figure optionsDownload as PowerPoint slide