Pr<SUP>3+</SUP>-Doped <I>β</I>-NaYF<SUB>4</SUB> for Temperature Sensing with Fluorescence Intensity Ratio Technique

Pure beta-NaYF4:0.8%Pr3+ powder sample was synthesized by the hydrothermal method. The temperature dependence of the fluorescence intensity ratio (FIR) of emission bands corresponding to the 3P1 --> 3H5 and 3P0 --> 3H5 transitions was measured in the temperature range of 120 K to 300 K excited by a 473 nm continuous wave (CW) laser. The dependence of the FIR on temperature is well fitted with an exponential function and the effective energy difference obtained is 457 cm(-1), which gives further an absolute temperature sensitivity of 0.01352 K(-1) at 300 K. The monotonous increase of FIR with temperature and high absolute temperature sensitivity demonstrate that this material can be used as temperature sensor. In addition, mono-dispersed NaYF4:1%Pr3+ nanoparticles were also synthesized.