Chunyan Cao

Tunable photoluminescence properties of Sr1‐yCayMoO4:Sm3+ phosphors (0 ≤ y < 1)

A series of Sr(1-x-y)CayMoO4:xSm(3+) (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors was synthesized by a conventional solid-state reaction method in air, and their structural and spectroscopic properties were investigated. The optimal doping concentration of Sm(3+) in SrMoO4:Sm(3+) phosphor is 5 mol%. Under excitation with 275 nm, in Sr(1-x-y)CayMoO4:xSm(3+) (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors, the emission band of the host was found to overlap with the excitation bands peaking at ~ 500 nm of Sm(3+) ion, and the energy transfer from MoO4 (2-) group to Sm(3+) ion can also be observed. The International Commission on Illumination (CIE) chromaticity coordinates of Sr(0.95-y)CayMoO4:0.05Sm(3+) phosphors with excitation 275 nm varied systematically from an orange (0.4961, 0.3761) (y = 0) to a white color (0.33, 0.3442) (y = 0.95) with increasing calcium oxide (CaO) concentration. However, Sr(0.95-y)CayMoO4:0.05Sm(3+) phosphors with excitation at 404 nm only showed red emission and the energy transfer between MoO4(2-) group to Sm(3+) ion was not observed. The complex mechanisms of luminescence and energy transfer are discussed by energy level diagrams of MoO4(2-) group and Sm(3+) ion.

Synthesis, optical properties, and energy transfer of Ce3+/Tb3+ co-doped MyGdFx (M = Li, Na, K)

Through a solid-state reaction method, the Ce(3+)/Tb(3+) co-doped MyGdFx (M=Li, Na, K; x=3, 4, 6; y=0, 1, 3) system samples have been synthesized by controlling the annealing temperatures and the ratios of raw materials. The samples were characterized by X-ray diffraction (XRD) patterns, photoluminescence (PL) excitation and emission spectra as well as luminescent dynamic decay curves. The experimental results suggest that the LiF is more difficult to react with the prepared material compared that of NaF or KF under similar reaction conditions. The samples crystallized in different crystalline phases. The energy transfer from Ce(3+) to Tb(3+) or Ce(3+) to Gd(3+) to Tb(3+) has been observed in all the samples. The Ce(3+) and Tb(3+) present different optical properties for they are sensitive to the local environment. In addition, the deduced lifetime of Tb(3+)(5)D4→(7)F5 transition decreases in the same system samples with the annealing temperature increasing. The deduced lifetime of Tb(3+)(5)D4→(7)F5 also decreases with the increase of the KF concentration in the KF system samples.

Ce3+/Tb3+ non-/single-/co-doped K-Lu-F materials: synthesis, optical properties, and energy transfer

Using a hydrothermal method, Ce(3+) /Tb(3+) non-/single-/co-doped K-Lu-F materials have been synthesized. The X-ray diffraction (XRD) results suggest that the Ce(3+) and/or Tb(3+) doping had great effects on the crystalline phases of the final samples. The field emission scanning electron microscopy (FE-SEM) images indicated that the samples were in hexagonal disk or polyhedron morphologies in addition to some nanoparticles, which also indicated that the doping also had great effects on the sizes and the morphologies of the samples. The energy-dispersive spectroscopy (EDS) patterns illustrated the constituents of different samples. The enhanced emissions of Tb(3+) were observed in the Ce(3+) /Tb(3+) co-doped K-Lu-F materials. The energy transfer (ET) efficiency ηT were calculated based on the fluorescence yield. The ET mechanism from Ce(3+) to Tb(3+) was confirmed to be the dipole-quadrupole interaction inferred from the theoretical analysis and the experimental data. Copyright

Synthesis, phase evolution and optical properties of Tb3+-doped KF–YbF3 system materials

KF-YbF3 system materials have been synthesized by a hydrothermal method without any surfactant or template. By controlling the reactant ratios of KF:Yb(3+), the hydrothermal temperature and the pH of the prepared solutions, the final products can evolve among the orthorhombic phase of YbF3, the cubic phase of KYb3F10 and the cubic phase of KYbF4. The X-ray diffraction (XRD) patterns of the samples prove the phase evolution of the final products. The morphologies of the samples were characterized using field emission scanning electron microscopy (FE-SEM) images and the evolution of the morphology is consistent with that of the crystalline phases. The optical properties of Tb(3+) in the samples were characterized by PL excitation and emission spectra, as well as luminescent decay curves.

Visible to near-infrared luminescence properties of Nd{sup 3+}-doped La{sub 2}BaZnO{sub 5} phosphor

La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphors are synthesized by a conventional high temperature solid state reaction method, and its crystal structure and luminescence properties are investigated. Photoluminescence bands peaking at ∼496, 540, 630, 670, 905, 1070, and 1350 nm of La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphors are observed at room temperature due to f–f transition of Nd{sup 3+} ion. The optimum Nd{sup 3+} doped concentration is ∼0.03. Lifetimes of La{sub 1.97}BaZnO{sub 5}:0.03Nd{sup 3+} phosphor with 496 and 1070 nm monitoring wavelengths are ∼280 and 250 µs, respectively. The luminescence mechanism is explained by using simplified energy lever diagram of Nd{sup 3+} ion. La{sub 2}BaZnO{sub 5}:Nd{sup 3+} material can be applied to powerful solid-state lasers as high efficient light sources. - Graphical abstract: PL spectra of La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphor in the visible and near-infrared regions and their corresponding to PLE at room temperature. - Highlights: • La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphor is synthesized. • PL spectrum is observed in the visible region. • PL spectrum is observed in the near-infrared region.