Photoluminescence and Judd-Ofelt analysis of Eu3+ doped akermanite silicate phosphors for solid state lighting

After aluminates, alkaline-earth silicates are the most researched category of luminescent inorganic phosphors. Eu3+ doped Ca2MgSi2O7 and Sr2MgSi2O7 phosphors synthesized by the combustion process. For the as-prepared phosphors, XRD and Rietveld refinement revealed a single phase with akermanite type structure belonging to tetragonal crystallography. UV–Vis spectroscopy was used to calculate the optical bandgap. Ca2MgSi2O7:x%Eu and Sr2MgSi2O7:x%Eu (x = 0.5 - 2.5) phosphors produced orange-red light with emission peaks at 590 nm, 614 nm, and 702 nm, which corresponded to the Eu3+ transitions 5D0 → 7F1, 5D0 → 7F2, and 5D0 → 7F4, respectively. Using a modified Judd-Ofelt technique based on the emission spectrum, the key spectroscopic properties (transition probabilities, radiative lifetimes, and branching ratios) associated with the 5D0 orange-red emitting level were found. Ω2 < Ω4 reveals that Eu3+ ions occupy high symmetry locations in the generated sample under the doping level studied in this work. There has also been a decrease in the Ω4 parameter. It implies that the 5D0 → 7F2 transition is more efficient than the 5D0 → 7F4. This indicates that the red color emission has been improved. The estimated CIE coordinates corroborated the PL emission in the orange-red region.