NaYF4:Yb3+/Ho3+ up-conversion luminescence and its low temperature sensing characteristics

Pure hexagonal [Formula: see text]-NaYF 4 micron crystals were synthesized by the hydrothermal method with the up-conversion luminescence properties studied by doping Yb[Formula: see text]/Ho[Formula: see text]. The up-conversion fluorescence spectra and fluorescence lifetime of [Formula: see text]-NaYF 4 micron crystals were determined by FLS-980 transient fluorescence spectrometer. By changing the doping concentration of Yb[Formula: see text]/Ho[Formula: see text], the optimal doping concentration was confirmed to be 20%Yb[Formula: see text]/2%Ho[Formula: see text]. The fluorescence spectrum was obtained by changing pump power, the relationship between power and intensity was analyzed, and the [Formula: see text]-NaYF 4 micron crystal green and red emission up-conversion process was obtained into a two-photon process. The 5 F[Formula: see text]I 8 and 5 S[Formula: see text]I 8 of the sample were thermally coupled to obtain a large absolute sensitivity (Sa) of low temperature. The maximum absolute sensitivity within the range of 64–194[Formula: see text]K is 0.0097[Formula: see text]K[Formula: see text] at 144[Formula: see text]K, while maximum absolute sensitivity at 333[Formula: see text]K is 0.00335[Formula: see text]K[Formula: see text] in the range of 293–493[Formula: see text]K. The experimental results show that the sensing characteristics of [Formula: see text]-NaYF 4 :Yb[Formula: see text]/Ho[Formula: see text] at low temperature are better than those at high temperature, and it has the potential to be used in the field of temperature sensing.