Effect of Li+ co-doping on structural and luminescence properties of Mn4+ activated magnesium titanate films

The effect of Li+ co-doping on crystal phase formation and photoluminescence (PL) of Mn4+ activated magnesium titanate films produced by a solid state reaction method at different temperatures (800–1200 °C) has been investigated by using X-ray diffraction (XRD), diffuse reflectance and PL spectroscopy. The chemical composition of sintered films was estimated by energy dispersive X-ray spectroscopy. The concentration of Mn impurity estimated by Electron spin resonance was about 5 × 1016 cm−3. The XRD study of the annealed films revealed several magnesium titanate crystal phases, such as Mg2TiO4, MgTiO3 and MgTi2O5. The contribution of each phase depended strongly on the annealing temperature and the presence of Li+ additive. Furthermore, Li+ co-doping facilitated the formation of both MgTiO3 and Mg2TiO4 phases, especially at lower annealing temperatures. The PL spectra showed two bands centered at 660 and 710 nm and ascribed to the 2E → 4A2 spin-forbidden transition of the Mn4+ ion in the Mg2TiO4 and MgTiO3, respectively. In Li co-doped films, the integrated intensity of Mn4+ luminescence was found several times stronger compared to Li-undoped films that was ascribed mainly to flux effect of lithium.