Novel efficient deep-red emitting phosphor SrCa2Ga2O6:Mn4+ with tululite-related structure

Mn4+-activated phosphors have been attracted to replace the rare-earth-activated phosphors in the use of deep-red optical devices. Owing to their low toxicity and wide applications, oxide materials are promising hosts for Mn4+ phosphors. Exploration into novel oxides is important for developing new Mn4+-doped phosphors with high luminescent efficiencies. In this study, we discovered the deep-red emitting phosphor SrCa2Ga2O6:Mn4+ in the Sr3Ga2O6-Ca3Ga2O6 solid solution system. From the single crystal X-ray diffraction analysis, SrCa2Ga2O6:Mn4+ was found to crystallize in a cubic unit cell with space group F432. Furthermore, SrCa2Ga2O6:Mn4+ was revealed to be a new member of tululite structure-related phosphors, such as Ca14Zn6Al10O35:Mn4+, Ca14Zn6Ga10O35:Mn4+, and Ca14Mg4Ga12O36:Mn4+. To study the fundamental luminescence properties, we synthesized SrCa2Ga2O6:Mn4+ powder samples via the conventional solid-state reaction method. SrCa2Ga2O6:Mn4+ has an absorption band in the region of 250-550 nm, and shows a deep-red emission band peaks at 712 nm. The excitation band is well matched to the emission wavelength of near-ultraviolet and blue light emitting diodes. The optimized sample exhibited high quantum efficiency and good thermal quenching properties. This study revealed SrCa2Ga2O6:Mn4+ has excellent potential as a deep-red emitting phosphor and is expected to be used for commercial applications, such as indoor plant cultivation and wavelength down-convertor for solar-cells.