[Synthesis and luminescence properties of Mg2Y8Si6O26 : Ce3+, Mn2+ phosphor].

Mg2Y8Si6O26 : Ce3+, Mn2+ phosphor was synthesized by the high temperature solid-state reaction, and the structure and luminescence properties were characterized by X-ray diffraction (XRD) and fluorescence spectrophotometer. The XRD pattern demonstrated that the synthetic material belongs to the hexagonal phase of Mg2Y8Si6O26 crystal without detectable impurity and space group P6(3)/m. The excitation and emission spectrum showed that there exist two lattice positions for Ce3+ in Mg2Y8Si6O26 crystal and their luminescence properties were compared. There are two emission peaks at 400 and 600 nm in the emission spectra under excitation at 286 nm, which come from Ce3+ and Mn2+ emission, respectively. It was demonstrated that there exists energy transfer between Ce3+ and Mn2+. The white light can be achieved by changing Mn2+ concentration. It can be used as a potential single-phased white phosphor excited by ultraviolet light.

[Synthesis and upconversion luminescence properties of BaIn6 Y2O13 : Yb3+, Er3+].

BaIn6 Y2O13 phosphors with different doping concentrations of Yb3+ and Er3+ were prepared via the high temperature solid-state reaction method. XRD data showed that BaIn6 Y2O13 phosphors belong to hexagonal system and the introduction of doping agent Yb3+ and Er3+ did not change the lattice structure of the host. The upconversion emission spectrum and power were measured by 971 nm LD laser with different excitation powers and the energy efficiencies of the samples were calculated. The obtained data showed that the ratio of green power to red power kept decreasing with the increase in doping agent concentration when the excitation density remains constant, increasing with the increase in the excitation density at the same concentration of doping agent. The analyses revealed that the former was attributed to the increasing cross relaxation between Er3+ ions, while the latter came from the raise of the energy transfer between Yb3+ and Er3+ ions and the excited state absorption of Er3+ ions due to the higher excitation density. With the increase in the excitation density, at the beginning the green luminescence power was proportional to the square of the excitation power, which agrees with the reported result. The maximum values of the fluorescence efficiencies of the samples were obtained as 0.38% (the doping concentrations of Yb3+ and Er3+ are 3%, 1%)and 0.06% (the doping concentrations of Yb3+ and Er3+ are 9%, 3%). It can be attributed to the long lifetime of 4 I13/2 energy level so it can gather a large number of electrons and reduce the population of ground state, resulting in lower pump efficiency.