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.