Er3+ doping YbTaO4 phosphors: Upconversion luminescence and temperature sensing characteristics

Trivalent erbium (Er3+) doped trivalent ytterbium (Yb3+) stoichiometric upconversion (UC) phosphors YbTaO4 (YbTaO4:Er3+) synthesized using the high temperature solid-state reaction method. The phase structure was analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM) and XRD Rietveld refinement methods. The vibration of the bonds was revealed through Fourier transform infrared (FT-IR) spectroscopy. The multi-photon UC green and red luminescence were investigated upon excitation with a 980 nm semiconductor laser, and the critical quenching concentration of Er3+ in the YbTaO4 stoichiometric host was derived as high as 15 at.%. The power-dependent UC emission spectra confirmed a two-photon population process for the UC green and red emissions. Furthermore, the temperature-dependent UC emission spectra were measured in the range of 300–570 K, and the optical temperature sensing performance of YbTaO4:Er3+ was demonstrated using the fluorescence intensity ratio (FIR) technique. The maximum absolute sensing sensitivity (SA) and relative sensing sensitivity (SR) of YbTaO4:Er3+ were determined as 0.0038 K-1 (@450 K) and 0.0102 K-1 (@300 K), respectively. These results suggest that Er3+ doped YbTaO4 stoichiometric phosphors hold great promise as upconversion materials for optical temperature sensing applications.