Multifunctional Ca2GaTaO6:Er3+ phosphors integrating multiband emission, optical temperature sensing, and WLED applications

Er 3+ -activated Ca 2 GaTaO 6 double-perovskite phosphors were synthesized by a high-temperature solid-state method and investigated for their structural and optical properties. X-ray diffraction and ionic-radius analysis confirm that Er 3+ ions preferentially replace Ca 2+ sites in the orthorhombic Pnma lattice, forming a stable single phase. Microstructural and XPS results verify uniform dopant distribution and the presence of oxygen-related defects beneficial to luminescence. Under 379 nm excitation, the phosphors exhibit strong green emission bands ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ) and a weaker red band ( 4 F 9/2 → 4 I 15/2 ). The optimal Er 3+ concentration ( x  = 0.02) achieves the highest emission intensity with a critical interaction distance of 11.5 nm, indicating quadrupole–quadrupole-type concentration quenching. Temperature-dependent up-conversion spectra show reliable fluorescence-intensity-ratio (FIR) behavior based on the thermally coupled 2 H 11/2 and 4 S 3/2 levels. The maximal absolute and relative sensitivities reach 1.17 %/K and 2.23 %/K, respectively, demonstrating excellent temperature-sensing capability comparable to other Er 3+ -based perovskites. Furthermore, the phosphor exhibits near-infrared emission around 1545 nm with similar concentration-dependent trends, indicating potential for dual-mode Visible/Near-infrared (NIR) detection. These results highlight Ca 2 GaTaO 6 :Er 3+ as a multifunctional luminescent material combining efficient green–red emission, competitive thermometric sensitivity, and NIR capability, showing promise for solid-state lighting and non-contact optical temperature sensing applications.