Coactivated cyan emitting phosphors in optical thermometry using thermally and non- thermally coupled levels

Abstract

The tunability in upconversion (UC) emission has been obtained with varying dopants concentration, visualized with a CIE chromaticity diagram and optimized in the cyan emitting region. The optical bistability has been observed in the Tm3+/Yb3+: MgWO4 phosphors. The CIE coordinates migrated towards the green region after doping Er3+ in the Tm3+/Yb3+: MgWO4 phosphors. The decay curve analysis of the developed phosphors has been performed. Thermally and non-thermally coupled levels of Er3+ and Tm3+ ions in the coactivated MgWO4 phosphors have been considered in the optical thermometry using the fluorescence intensity ratio (FIR) approach. The addition of Er3+ and Li+ in Tm3+/Yb3+: MgWO4 phosphors improves the sensitivity of luminescence thermometry. The absolute and relative sensitivity in the non-thermally coupled levels is found maximum as compared to the system containing thermally coupled levels.