Site-Selective Occupation for Broadband Upconversion Luminescence in Ca3Y(GaO)3(BO3)4:Yb3+,Mn2+ Phosphors

A room-temperature yellow emission band around 600 nm is obtained in Yb3+ and Mn2+ codoped Ca3Y­(GaO)3(BO3)4 with near-infrared laser excitation. The structure analysis, excitation, and emission spectra are investigated in detail to elucidate the relevant luminescence mechanisms. The spectral analysis demonstrates that the orange broadband emission under 410 nm excitation originated from Mn2+ ions occupying two kinds of Ca sites with different crystal field environments, while the yellow emission band upon 980 nm laser excitation is ascribed to Mn2+ ions located only at a specific low-coordinated Ca site. The suggested upconversion mechanism of yellow emission is dominated by the ground state absorption and excited state absorption (GSA/ESA) processes of Yb3+–Mn2+ pairs. The efficient broadband upconversion luminescence in Ca3Y­(GaO)3(BO3)4:Yb3+,Mn2+ offers significant insight into exploring novel transition metal ions based UC materials for lighting and displays.