Hydrothermal synthesis and luminescent properties of Ca3(PO4)2: Dy3+ white-emitting phosphors

Highlights: • The white-emitting Ca₃(PO₄)₂: Dy³⁺ phosphors were synthesized via the hydrothermal synthesis. • The precursor at pH of 7 matches well with Ca₄P₂O₉. • The changes of phase structure, morphology, luminescent properties of the phosphor by controlling pH value and calcination temperature was systematically studied. • As the pH value in the initial reaction solution increased, the morphology of the samples changed from long-rod to short-rod and sphere and the size reduced. -- Abstract: The white-emitting Ca₃(PO₄)₂: Dy³⁺ phosphors were prepared via hydrothermal synthesis. The phosphors were characterized by XRD, TEM, SEM, EDS, GSAS structural refinement and PL spectroscopy, respectively. Rietveld refinement demonstrated that the Ca₃(PO₄)₂ crystal structure consisted of [PO₄] tetrahedrons filled with Ca atoms. Dy³⁺ ions occupied high-symmetry sites due to the emission intensity of ⁴F_9/2 → ⁶H_15/2 was strongest. Moreover, the pH value and calcination temperature had important effects on the phosphor morphology and luminescent properties. The morphology of the samples changed from long-rod to short-rod and sphere and the size reduced as the pH value in the initial reaction solution increased. The samples with pH of 7 had the best luminescence properties, and the precursor before calcination corresponded to Ca₄P₂O₉. With the calcination temperature of the precursor with pH of 7 increased, the phosphor morphology changed from nanorods to grains with diameters of about 1 μm, and the luminescence properties were improved continuously. The CIE coordinate of Ca₃(PO₄)₂: Dy³⁺ phosphor was (0.283, 0.343). The Ca₃(PO₄)₂: Dy³⁺ phosphor has better application prospects for white light-emitting diodes.