Up-conversion luminescence and optical temperature sensing behaviour of Yb3+/Er3+ codoped CaWO4 material

Present article report on structural and optical properties of Er3+/Yb3+ codoped CaWO4 phosphors. Structural properties are explored using XRD and Raman technologies. The upconversion emission has been investigated with 980 nm excitation. The upconversion emission intensity is dependent on the concentrations of Yb3+ ions and reaches a maximum at 7%. Logarithmic plots of power dependencies reveal that the green and red emissions originate from a two-photon upconversion process. Based on the photon energy and the emission spectra, the possible upconversion processes and emission mechanisms are discussed. Finally, the optical temperature sensing properties has been performed using the fluorescence intensity ratio technique based on green upconversion emissions. Its temperature sensitivity is found to be above 0.0025 K-1 in the whole temperature range of 300-540 K, revealing this phosphor to be a promising optical temperature sensing material.