Hydrothermal synthesis of BaLu 2 F 8 :Ln 3+ crystals: phase/morphology evolution, energy transfer and tunable multicolor luminescence

BaLu 2−x F 8 : x Ln 3+ crystals have been synthesized via a one-step hydrothermal route without any surfactants. X-ray diffraction (XRD), scanning electron microscopy (SEM), and down-shift/up-conversion photoluminescence spectroscopy were used to characterize the samples. Pure monoclinic BaLu 2 F 8...

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Veröffentlicht in:CrystEngComm 2020-07, Vol.22 (29), p.4862-4874
Hauptverfasser: Xiong, Jie, Wang, Wei, Mao, Yini, Liu, Qingyuan, Yang, Jun, Tang, Jianfeng, Hu, Shanshan
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Sprache:eng
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Zusammenfassung:BaLu 2−x F 8 : x Ln 3+ crystals have been synthesized via a one-step hydrothermal route without any surfactants. X-ray diffraction (XRD), scanning electron microscopy (SEM), and down-shift/up-conversion photoluminescence spectroscopy were used to characterize the samples. Pure monoclinic BaLu 2 F 8 crystals were obtained at pH = 7 with NaBF 4 as a fluoride source. Doping 0.06 mmol Ln 3+ ions from Ho 3+ to La 3+ and doping Yb 3+ ions from 0.1 to 0.4 mmol both have caused dramatic changes to the product's morphology from prismatic microrods of about 10 μm to particles of about 3 μm aggregated by flakes. The differences in the phase, size and shape of the final products were greatly related to the fluoride source and pH values, which have been studied in detail. In addition, surfactants also affected the phase and morphology of the BaLu 2 F 8 crystals. Multicolor down-shift emission was achieved in the BaLu 1.94 F 8 :0.06Ln 3+ (Ln = Sm, Eu, Tb, Dy, Er and Tm) crystals under UV lamp excitation at 365 nm, and multicolor UC luminescence has been achieved in BaLu 2 F 8 :Yb 3+ ,Ln 3+ (Ln = Er, Tm, Ho) systems. When the Yb 3+ –Er 3+ ions are co-doped into the host, the mechanism for the red emission ( 4 F 9/2 → 4 I 15/2 ) retains the tri-photon process like the single-doped Er 3+ ion, but the mechanism for the green emission ( 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ) is a two-photon process. Furthermore, the UC luminescence mechanism for the co-doped Yb 3+ –Ho 3+ pairs is also a tri-photon process in the BaLu 2 F 8 matrix. The as-prepared BaLu 2 F 8 :Ln 3+ phosphors have potential applications in the fields of light emitting devices, three-dimensional displays and backlights.
ISSN:1466-8033
1466-8033
DOI:10.1039/D0CE00818D