Photoluminescence property, energy transfer mechanism, and optical thermometric behavior of bismuth-europium codoped disordered melilite-type phosphor

In the pursuit of optical thermometers, the fluorescence intensity ratio technique has aroused much interest because of the urgent need for noncontact thermometers driven by technological development. Here, an optical thermometer BaLaGa3O7:Bi3+,Eu3+ based on different thermal responses of Eu3+ and Bi3+ emissions had been reported. The structure, morphology, luminescence properties, and optical thermometric behavior were investigated by experimental data comprising X-ray diffraction patterns, microscopy, and luminescence spectroscopy. The dopants with eight oxygen ligands in the melilite-type host form emission centers. The Bi3+ singly doped, and Eu3+ singly doped phosphors can have intense blue and red emissions due to the 3P1-1S0 and 5D0-7FJ(0−4) electron transitions, respectively. In the Bi3+-Eu3+ codoped phosphors, tunable emission colors were obtained owing to Bi3+→Eu3+ energy transfer and doping concentration variation. Moreover, the intensity ratio of Bi3+ and Eu3+ emissions varied with the temperature in the range of 298 − 523 K. The relative and absolute sensitivities of the as-prepared phosphor were determined to be 0.29%K−1 and 0.20%K−1, respectively, manifesting that the prepared BaLaGa3O7:Bi3+,Eu3+ has the potential to serve as phosphors for optical thermometers.