Design of core–shell phosphors with tunable luminescence and improved thermal stability by coating with g-C3N4

Abstract

The exploration of new strategies to fabricate phosphors with tunable luminescence and enhanced thermal stability has been pursued since a long time. In this study, we propose and demonstrate a novel methodology of coating g-C₃N₄ on phosphors by a vapor deposition method to synthesize core–shell phosphors with tunable luminescence and improved thermal stability. By this method, flaky g-C₃N₄ can be evenly coated on the surface of the precursors Y₂O₃:Eu³⁺,Tb³⁺ and Y₂O₃:Eu³⁺,Tb³⁺@SiO₂ with a thickness of 8 nm. Under the excitation at 368 nm, the CIE coordinates can be adjusted from blue region (0.1713, 0.1887) to white (0.3074, 0.3232) and yellow (0.4565, 0.4703) regions by controlling the amount of g-C₃N₄. Moreover, the thermal stability of phosphors can be improved by the g-C₃N₄ coating shell at elevated temperatures due to the isolation of luminescence centers, modification of surface defects, and efficient energy transfer from g-C₃N₄; the emission intensity of Eu³⁺ at 398 K improved by 13% after coating with g-C₃N₄. The above-mentioned effects of g-C₃N₄ were also proved to work well on the Ca_9.5Na₂(PO₄)₇:Eu²⁺ yellow-green emitting phosphor, indicating that this methodology has general applicability for improving luminescent properties of phosphors.