Luminescence and thermometric properties of Ba2LaSbO6:Eu3+/g-C3N4 mixed materials

In this study, a series of Ba ₂ La _{1 −  x} SbO ₆ : x Eu ³⁺ ( x  = 0, 0.05, 0.10, 0.15, 0.20, 0.25) phosphors and graphitic carbon nitride (g-C ₃ N ₄ ) powders were synthesized via high-temperature solid-phase method. Their structural and luminescent properties were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectra. Upon excitation at 273 nm, Ba ₂ LaSO ₆ :Eu ³⁺ exhibits pronounced red emission, demonstrating anti-thermal quenching behavior within temperature range of 313–453 K. At 453 K, its emission intensity reaches 131.3% of its initial intensity measured at 313 K. In contrast, g-C ₃ N ₄ shows rapid thermal quenching, with emission intensity dropping to 7.6% at 573 K compared to that at 313 K. A mixed material, prepared with an optimal mass ratio of 1:1.5 between Ba ₂ LaSO ₆ :0.1Eu ³⁺ and g-C ₃ N ₄ , demonstrates dual-mode thermometric performance. Using fluorescence intensity ratio (FIR), the maximum absolute sensitivity ( S _a ) and relative sensitivity ( S _r ) are determined to be 1.34% K ^− 1 (522 K) and 1.53% K ^− 1 (368 K), respectively. Temperature characterization using color coordinate (CIE) shifts achieves maximum S _a and S _r values of 0.12% K ^− 1 (313 K) and 0.44% K ^− 1 (313 K), respectively. Additionally, the mixed material exhibits excellent repeatability, achieving repeatability parameter ( R ) of 98.8% for FIR and 98.9% for CIE measurements across five temperature cycles. These results underscore potential of the mixed material for self-calibrating optical thermometers.