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

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.

Automated summary

The tunability of upconversion emission was achieved by varying dopant concentration and optimized in the cyan emitting region. Optical bistability was observed in Tm3+/Yb3+: MgWO4 phosphors. The CIE coordinates shifted towards the green region upon Er3+ doping. Decay curve analysis was performed for the developed phosphors. The optical thermometry using the fluorescence intensity ratio (FIR) approach considered the thermally and non-thermally coupled levels of Er3+ and Tm3+ ions in the coactivated MgWO4 phosphors. The addition of Er3+ and Li+ improved the sensitivity of luminescence thermometry in Tm3+/Yb3+: MgWO4 phosphors, with higher sensitivity observed in the non-thermally coupled levels compared to the thermally coupled levels.