Abstract: A series of YPO₄∶Dy³⁺ phosphors with different Li⁺ doping concentrations were synthesized via a hydrothermal method combined with high-temperature calcination. The effects of Li⁺ co-doping on the structure， morphology and luminescence properties of YPO₄∶Dy³⁺ phosphors were systematically investigated. X-ray diffraction （XRD） results indicate that Li⁺ doping promotes the phase transition of YPO₄·0.8H₂O from hexagonal to tetragonal phase. Moreover， Li⁺ could either substitute Y³⁺ at lattice sites or occupy interstitial positions. Scanning electron microscopy （SEM） results show that with the increase of Li⁺ doping concentration， the morphology of the phosphor changes from hexagonal prism to spherical particles， and the average particle size gradually decreases. Fluorescence spectroscopy analysis reveals that appropriate Li⁺ doping can significantly enhance the luminescence intensity of YPO₄∶Dy³⁺ phosphors. When the Li⁺ doping amount is 5%， the luminescence intensity reaches the maximum value， which is approximately 2.3 times that of the undoped sample. Meanwhile， Li⁺ doping can also improve the thermal stability of the phosphor. With the increase of Li⁺ doping amount （x=1%~7%）， the CIE chromaticity coordinates of YPO₄∶5%Dy³⁺，xLi⁺ phosphors change gradually from （0.233， 0.283） to （0.238， 0.289）. The research results demonstrate that Li⁺ co-doping is an effective approach to regulate the luminescence properties of YPO₄∶Dy³⁺ phosphors， and provides theoretical basis and experimental foundation for their application in the field of white light-emitting diodes （LEDs）.

Key words: yttrium phosphate; alkali metal; Dy³⁺ doping; phase transition regulation; luminescence performance