Upconversion Luminescence, Laser Heating Effect and Temperature Sensing Properties of β-BiNbO4:Er3+/Yb3+

Upconversion (UC) phosphors of beta-BiNbO4:Er3+/Yb3+ as temperature sensing materials were synthesized using the solid-state method. The structure was characterized by x-ray diffraction (XRD), revealing that all samples exhibited a single triclinic phase. Upon 980 nm laser excitation, the phosphors exhibited strong green emission and relatively weak red emission. Its possible luminescence mechanism is discussed based on the dependence of the UC emission spectra on the pump laser power. Finally, its temperature sensing properties were investigated using the temperature-dependent fluorescence intensity ratio (FIR) of two green emission bands originating from Er3+ ions. The thermal effect from laser irradiation and its influence on temperature sensing were also studied. Its absolute sensitivity S-A exhibited a smaller change above 300 K, and reached a maximum value of 5.5 parts per thousand K-1 around 400 K. These results indicate that this type of qualified UC phosphor shows potential application in optical temperature sensors, especially at high temperature.