Optical Temperature Sensing of YbNbO4:Er3+ Phosphors Synthesized by Hydrothermal Method

The novel YbNbO4:Er3+ phosphors were firstly synthesized through the hydrothermal method by adding LiOH·H2O as flux in the H2O/EG system. YbNbO4:Er3+ phosphors showed the agglomerated irregular polygons coexisting with some tiny grains. XRD and Raman spectra were measured to understand the phase structure and the crystal growth mechanism of YbNbO4:Er3+ phosphors. The upconversion (UC) emission spectra, the pump power dependency and UC mechanism were studied under 980 nm excitation. Based on the fluorescence intensity ratio technique, YbNbO4:Er3+ exhibited the maximum sensor sensitivity of 0.00712 K−1 at 220 K, providing a promising application in optical low-temperature sensors.