Energy transfer processes leading to strong NIR-to-red upconversion in the Yb-concentrated Sr3Yb0.98Er0.02(PO4)3 eulytite - Hu, X.; Piccinelli, F.; Ruggieri, S.; Camarero Linares, P.; Haro, P.; Bettinelli, M. (Optical Materials: X, 2024)