Siling Guo

Synthesis and luminescence properties of novel deep red emitting phosphors Li2MgGeO4:Mn4+

Novel deep red phosphor Li2MgGeO4:Mn4+ is synthesized by high temperature solid state reaction method in air. The strongest PL band peaking at ~ 671 nm in the range of 600–750 nm is due to the 2E → 4A2 transition of Mn4+ ion and the PLE spectra shows broad band peaking at ~ 323 within the range 220–550 nm owing to the 4A2 → 4T1 transitions of Mn4+ ion. The optimum Mn4+ doping concentration is about 0.4 mol.%. The luminous mechanism is explained by Tanabe–Sugano diagram of Mn4+ ion. The results indicate that red phosphor Li2MgGeO4:Mn4+ is a beneficial phosphor for use in white light-emitting-diodes (LEDs).

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.

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.