YF₃:RE³⁺ (RE = Dy, Tb, Eu) Sub-microstructures: Controllable Morphology, Tunable Multicolor, and Thermal Properties

A series of emission-tunable YF 3:RE 3+ (RE = Dy, Tb, Eu) phosphors were first synthesized by a glutamic acid-assisted one-step hydrothermal process. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the samples were YF 3 and Na(Y 1.5 Na 0.5 )F 6 and the size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions or by adjusting the RE 3+ /NaF ratio or RE 3+ /NaBF 4 ratio. The morphologies for the products include bundlelike microstructures, fantail-like shape, microspindles, irregular bulk, walnutlike shape, irregular ellipsoidal microrods, the asymmetric hexagonal-prismatic tubular structures and irregular microrods and irregular nanoparticles and microsphere. Furthermore, the photoluminescence properties of YF 3:Dy 3+,Tb 3+ and YF 3:Tb 3+,Eu 3+ were investigated in detail. Blue and yellow emissions corresponding to the 4 F 9/2 → 6 H 15/2 (475 nm), 4 F 9/2 → 6 H 13/2 (570 nm) transition of Dy 3+; blue and green emissions corresponding to the 5 D 4 → 7 F 6 (488 nm), 5 D 4 → 7 F 5 (542 nm) transition of Tb 3+; and red emissions corresponding to the 5 D 0 → 7 F 1 (591 nm), 5 D 0 → 7 F 2 (614 nm), and 5 D 0 → 7 F 4 (698 nm) transition of Eu 3+ can be observed in YF 3 host under 365 nm near-ultraviolet radiation. The energy transfer process from Dy 3+ to Tb 3+ and from Tb 3+ to Eu 3+ was demonstrated to be resonant type via a quadrupole–quadrupole mechanism. Additionally, when codoping Tb 3+ with Dy 3+ or Eu 3+ or tridoping Dy 3+, Tb 3+, and Eu 3+ ions in the single component, colorful emitting can be obtained, giving abundant blue, green, yellow, orange, and especially white light emission. The temperature-dependent photoluminescence for as-prepared phosphors has been investigated in detail. Importantly, it is found that the fluorescent intensity ratio of YF 3:5%Dy 3+,2%Tb 3+,2%Eu 3+ displays a linear correlation with temperature in the wide range of 298–398 K with a high sensitivity of 0.24% K –1, indicating that it could be a good candidate for ratiometric optical thermometry. All these properties indicate that the developed phosphor may potentially be used as single-component multicolor-emitting phosphors.