Optical and structural properties of Mn-doped magnesium titanates fabricated with excess MgO. (June 2021)

• Record Type: Journal Article
• Authors: Borkovska, L.; Khomenkova, L.; Stara, T.; Vorona, I.; Nosenko, V.; Gudymenko, O.; Kladko, V.; Kozoriz, K.; Labbé, C.; Cardin, J.; Doualan, J.-L.; Kryshtab, T.
• Is Part Of: Materials today communications. Volume 27(2021)
• Publication Date: 2021-06
• Subjects: Oxide materials -- Ceramics -- Point defects -- Luminescence -- Electron paramagnetic resonance -- X-ray diffraction; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2021.102373
• Languages: English
• ISSNs: 2352-4928

Abstract

Graphical abstract: Highlights: Ceramics based on Mn-doped MgTiO3 was produced by solid state reaction approach. In MgTiO3 sintered under equimolar MgO:TiO2 ratio, Mn incorporates mainly as Mn 2+ . Ceramics produced with excess MgO composes of MgTiO3 and Mg2 TiO4 phases. Mg2 TiO4 phase is under compressive strains and shows modified Mn 4+ red luminescence. The excess MgO facilitates incorporation of Mn onto Ti 4+ site in MgTiO3 phase. Abstract: Optical and structural properties of ceramics based on Mn-doped magnesium titanates synthesized by sintering in air at 1200 °C of MgO and TiO2 powders of different molar ratios ranging from MgTiO3 to Mg2 TiO4 stoichiometric compositions were studied. The influence of excess MgO on Mn incorporation in crystal lattice of MgTiO3 was also investigated. The Mn 4+ ions substituted Ti 4+ sites were controlled by the photoluminescence (PL) and diffuse reflectance spectroscopy, and the Mn 2+ ions on Mg 2+ sites were monitored by electron paramagnetic resonance (EPR). The ceramics produced using equimolar ratio of MgO and TiO2 composed of a major MgTiO3 and a minor MgTi2 O5 crystal phases, and those made with excess MgO contained MgTiO3 and Mg2 TiO4 phases in different proportions. The EPR study showed that Mn incorporated in MgTiO3 synthesized under 1:1 M ratio as Mn 2+ ion mainly. This agreed with low intensity of Mn 4+ red PL ascribed to low concentration of Mn 4+ centers and partial absorption of the UV excitation light by the MgTi2 O5 phase. The Mn-doped MgTiO3 synthesized with excess MgO of 19 and 50 mol.% showed increased Mn 4+ red PL by a factor 30–50, enhanced Mn 4+ optical absorption and more than ten times decreased Mn 2+ EPR signal. The Mg2 TiO4 phase was found to be under compressive strains attributed to the presence of Mg vacancies and demonstrated Mn 4+ red PL with modified spectrum shape and decay behavior. It is concluded that in MgTiO3 the excess MgO facilitates the incorporation of Mn onto Ti 4+ site and can be used for the increasing of Mn 4+ PL intensity.