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

Abstract In this study, a series of Ba₂La1 − xSbO₆:xEu³⁺ (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) phosphors and graphitic carbon nitride (g-C₃N₄) 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, Ba₂LaSO₆:Eu³⁺ 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-C₃N₄ 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 Ba₂LaSO₆:0.1Eu³⁺ and g-C₃N₄, demonstrates dual-mode thermometric performance. Using fluorescence intensity ratio (FIR), the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) 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 Sa and Sr 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.