Synthesis of near-white emission phosphors for luminescence lifetime thermometers and flexible security films

Novel near-white emission phosphors of single Pr³⁺-doped Ca₂(Gd,Y)TaO₆ double perovskites were successfully prepared. Their crystal structures, morphologies, elemental compositions, photoluminescence (PL) behaviors, internal quantum yields, thermal stabilities, etc. were systemically investigated. Interestingly, the chemical composition of Gd³⁺ ions replaced by Y³⁺ ions did not affect the crystal structure of the monoclinic structure in the P 21/n(14) space group. Particularly, the PL emission spectrum of the optimal Ca₂YTaO₆:Pr³⁺ phosphors showed different dominant peaks compared to the Ca₂GdTaO₆:Pr³⁺ phosphors due to the appearance of cross-relaxation. Note that the near-white region chromaticity coordinates/internal quantum yields of the optimal Ca₂GdTaO₆:Pr³⁺ and Ca₂YTaO₆:Pr³⁺ phosphors were (0.363, 0.438)/28.1 % and (0.350, 0.441)/27.4 %, respectively. Finally, the potential applications of single Pr³⁺-doped double-perovskite phosphors were expanded to luminescence lifetime thermometers and flexible safety film applications.