Down- and upconversion luminescence in Er3+ doped CaYAl3O7

The Er³⁺-doped materials have been intensively studied for applications in lighting, communication technologies, luminescence thermometry, anti-counterfeiting, solid-state lasers, etc. Er³⁺-doped materials demonstrate multi-mode luminescence excited with UV, Vis, and NIR radiation, opening a diverse field of applications in anti-counterfeiting, luminescence thermometry, etc. The properties of melilite-type phosphor CaYAl₃O₇ doped with Er³⁺ ions have been studied for optical and optoelectronic applications. The samples were synthesized using the high-temperature solid-state method and analysed by X-ray diffraction and optical spectroscopy techniques in the 8.5-300 K temperature range. The down-conversion and upconversion luminescence in Er³⁺-doped CaYAl₃O₇ was observed. At 8.5 K, the green emission at 552.4 nm increased 7.4 times in intensity compared to the room temperature, and the fluorescence intensity ratio (FIR) of 552.5nm/525.1 nm bands increased from 1.4 to 293.5 at 8.5 K offering applications of CYA:Er³⁺ in luminescence thermometry. The dominating mechanism of upconversion luminescence in the studied CYA:Er³⁺ powders is the excited-state absorption (ESA). The contribution of cross-relaxation processes in the Er³⁺ emission in the red spectral range (at 645- 690 nm) was detected. The possibility of exciting CYA:Er³⁺ luminescence by UV, VIS, and NIR radiation makes CYA:Er³⁺ a promising component in technologies for anti-counterfeiting applications.