Enhanced upconversion luminescence and fluorescence thermometry of Sc2Mo3O12:Yb/Er by Al3+ doping

Lanthanide ion-doped Sc 2 Mo 3 O 12 upconversion (UC) luminescent materials exhibit a unique negative thermal quenching phenomenon, making them highly promising for applications in fluorescence thermometry. However, the luminescence intensity of Sc 2 Mo 3 O 12 phosphor is relatively low at room temperature, so it is urgently necessary to enhance the intensity of the phosphor at room temperature. In this study, Sc 2 Mo 3 O 12 :Yb/Er/Al phosphors were synthesized via the solid-state reaction method, and the effects of Al 3+ ion doping on their phase composition and upconversion fluorescence properties were investigated by X-ray diffraction (XRD) analysis and upconversion fluorescence spectra evaluation. The results show that the incorporation of Al 3+ ions enhanced the UC intensity at room temperature and improved the fluorescence thermometry performance. The doping of Al 3+ ions disrupts the lattice symmetry and reduces the distance between sensitizer ions (Yb 3+ ) and activator ions (Er 3+ ), increasing the UC intensity by approximately 4.2 times. In addition, the dependence of fluorescence properties of ScAl 0.6 Mo 3 O 12 :18%Yb 3+ /2%Er 3+ samples on temperature were tested, the negative thermal quenching effect was verified, and the thermal enhancement mechanism was explored. The maximum absolute and relative sensitivities of the ScAl 0.6 Mo 3 O 12 :18%Yb 3+ /2%Er 3+ reached 0.00635 K −1 at 372 K and 0.00829%K −1 at 300 K, respectively, indicating the potential of the phosphor for applications in optical thermometry.