Li+ aided self-activated [formula omitted] phosphors for efficient dual-mode emission and temperature sensing application

Abstract

For the first time, lanthanide co-doped self-activated Ca9Y1−x−yErxYby(VO4)7 phosphors have been investigated for bearing dual-mode emission: downshifting and upconversion emission behavior. The Ca9Y1−x−yErxYby(VO4)7 phosphor, under 379 nm excitation evinces two bright green emission peaks at 525 nm and 553 nm, which corresponds to H11/22,S3/24→I15/24 transitions of Er3+ ion, this transition is sensitized by an efficient energy transfer from the (VO4)3− group to Er3+ ions. Irradiated with a 980 nm power tunable laser, it shows strong green and comparatively weak red emissions bands. The upconversion emission can be enhanced enormously with the introduction of Li+ ions in the optimized Ca9Y0.847Er0.003Yb0.15(VO4)7 phosphor. Furthermore, utilizing the well-known fluorescence intensity ratio (FIR) technique, optimized Ca9Y0.647Li0.20Er0.003Yb0.15(VO4)7 phosphor has been explored for optical temperature sensors also. The maximum absolute sensitivity and relative sensitivity are obtained to be 0.0125 K−1 at 513 K and 0.012 K−1 at 300 K, respectively. The acquired result reveals that the phosphor Ca9Y0.647Li0.20Er0.003Yb0.15(VO4)7 can be a worthy material for temperature sensing application.