Interacting layered hydroxide nanosheets with KF leading to Y/Eu hydroxyfluoride, oxyfluoride, and complex fluoride nanocrystals and investigation of photoluminescence
2017
Li, Jing | Wang, Xuejiao | Zhu, Qi | Kim, Byung-Nam | Sun, Xudong | Li, Ji-Guang
Treating nanosheets (∼4 nm thick) of RE₂(OH)₅NO₃·nH₂O layered hydroxyl nitrate (LREH-NO₃⁻, RE = Y₀.₉₅Eu₀.₀₅) with KF solution at a low temperature of ∼90 °C yielded F⁻-substituted LREH (RE₂(OH)₅F·nH₂O), RE(OH)₃₋ₓFₓ hydroxyfluoride (x = 1.15–1.51), and K₅RE₉F₃₂ complex fluoride depending on the F/RE molar ratio (R) used for phase conversion (R = 3 : 3–200 : 3). Calcining RE(OH)₃₋ₓFₓ of a relatively high F content (x = 1.29–1.51, R = 40 : 3–70 : 3) at 450 °C in air produced REO₍₃₋ₓ₎/₂Fₓ oxyfluorides, with the F/RE molar ratio close to that of the orthorhombic structured Y₅O₄F₇ phase. Oxidation of REO₍₃₋ₓ₎/₂Fₓ to form REOF and even RE₂O₃ was observed at temperatures above ∼700 °C. The materials were characterized in depth by the combined techniques of elemental analysis, XRD, FE-SEM, TEM, FTIR, and TG to reveal the process of composition, phase, and morphology evolution, and the photoluminescent properties of the resultant hydroxyfluoride, oxyfluoride and complex fluoride were also elaborated with regard to the crystal structure of the host lattice, F content, and the temperature of calcination.
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