Pure red upconversion luminescence and optical thermometry of Er3+ doped sensitizer-rich SrYbInO4 phosphors

Er³⁺ doped sensitizer-rich SrYbInO₄ upconversion phosphors with an orthorhombic structure (Pnma) were synthesized by using a high temperature solid state reaction and their phase structure, site occupation and microstructure have been analyzed. Interestingly, upon the excitation from 980 nm pulsed laser diodes, the SrYbInO₄:Er³⁺ phosphor emitted a nearly pure red emission on account of the ⁴F_9/2 → ⁴I_15/2 transition of Er³⁺. Additionally, based on the pump power dependence of the upconversion intensity and the schematic diagram of the energy levels, the upconversion mechanism in this system was verified in a two-photon process. The temperature-dependent behaviors of the as-synthesized sample demonstrated the potential for applications in optical thermometry.