Two-step synthetic route towards Er3+/Yb3+ co-doped vernier yttrium oxyfluoride phosphor with high optical temperature sensing sensitivity

Abstract Exploring an up-conversion (UC) phosphor for the fluorescence intensity ratio (FIR) technique has been a great challenge in the field of optical temperature sensors. In this paper, a two-step synthetic route [Y(OH)CO3→Y(OH)1.63F1.37→Y6O5F8] was designed to successfully synthesize Y6O5F8:Yb3+/Er3+ UC phosphors for optical temperature sensing. The phase and morphology of the samples at various stages of the synthetic route were investigated. Under 980 nm excitation, two green emission bands centered at 522 nm and 547 nm and a red emission band centered at 670 nm were observed. Y6O5F8:10%Yb3+/1%Er3+ exhibited the strongest UC emission under 980 nm excitation and was selected for further characterizations. The absorption and emission processes (a two-photon process) of photons in Y6O5F8:10%Yb3+/1%Er3+ were elucidated based on the UC luminescence mechanism. Among them, the ET occupies a key position, which was also confirmed by the decay curves. In addition, the optical temperature sensing behavior of Y6O5F8:10%Yb3+/1%Er3+ was explored using the FIR technique. The maximum absolute and relative sensitivities were determined to be 0.0074 K-1 (518 K) and 1.39% K−1 (293 K), respectively. The results show that Y6O5F8:10%Yb3+/1%Er3+ phosphor has promising application potentials in optical temperature sensors with excellent sensitivity.