Multifunctional optical applications in CaLaGaO4:Er3+ phosphors

To construct high-performance green fluorescent media suitable for non-contact optical temperature measurement and information anti-counterfeiting, excellent fluorescence thermal stability phosphors are required. In this paper, CaLa 1- x GaO 4 : x Er 3+ phosphors were synthesized using a high-temperature solid-state method. When excited at 378 nm, the optimized CaLaGaO 4 :2%Er 3+ sample yielded efficient downshifting luminescence, with prominent green bands centered at 523 and 552 nm originating from the 2 H 11/2  →  4 I 15/2 and 4 S 3/2  →  4 I 15/2 transitions, respectively. Weak red emission near 669 nm, attributed to the 4 F 9/2  →  4 I 15/2 transition, was also observed. Leveraging fluorescence intensity ratio methodology based on thermally coupled energy levels ( 2 H 11/2 and 4 S 3/2 ) for non-contact optical temperature measurements, the system yielded a maximal relative sensitivity of 1.97% K −1 at 298 K, while the absolute sensitivity reached 0.89% K −1 at 473 K, highlighting its superior thermal sensing properties. Moreover, the refined luminescent powders were blended with polyvinyl alcohol (PVA) to formulate a security printing medium. This ink remains colorless under ambient illumination; however, upon exposure to 365 nm ultraviolet radiation, it distinctly exposes concealed alphanumeric characters and designs. Consequently, this system exhibits significant applicability within the domain of optical information encryption and forgery prevention. The synergistic combination of efficient downshifting luminescence and high temperature measurement sensitivity establishes the potential of synthesized CaLaGaO 4 :Er 3+ phosphors as a multifunctional platform for luminescence sensing.