Non-contact ratiometric thermometer of NaLuF4: Yb3+/Er3+ phosphors based on multi-phonon assisted excitation

NaLuF4: Yb3+/Er3+ phosphors are synthesized via a hydrothermal method. The photoluminescence properties of the phosphors are researched at a temperature range from 296 to 461 K under 1064 nm excitation. Fluorescence intensity ratio I/I0 shows a linear relationship with increasing the temperature from 296 to 420 K. The maximum sensitivity is obtained to be 0.0194 K-1 using non-contact ratiometric thermometer through multi-phonon assisted excitation.