Performance improvement of temperature sensor based on rare-earth ion fluorescence by using KBr-diluted phosphor

We exemplify the Er(NbO₃)₃ phosphor to demonstrate that the performance of the temperature sensor based on thermal effect of fluorescence intensity ratio (FIR) of 980-nm-upconverted Er³⁺ green 530 and 550 nm emissions can be improved by using KBr-diluted phosphor. The sensing performance of the diluted phosphor plate was studied as a function of KBr:Er(NbO₃)₃ molar ratio from 0:1 to 100:1. The results show that the KBr dilution enables to enhance the fluorescence intensity and increase the temperature sensitivity. Meanwhile, the KBr itself does not affect either the Er³⁺ spectroscopic properties or the FIR value. There is an optimum KBr: Er(NbO₃)₃ molar ratio within 15:1 and 20:1, for which the 530 (550) nm signal increases by 30% (20%) and the relative sensitivity at the physiological temperature increases by 14%.