[A novel red phosphor (La3PO7:Eu3+) prepared by solid state method].

Novel red phosphor, Eu3+ -doped oxyphosphate (La3 PO7:Eu3+), was synthesized by a solid state method under high temperature. All the starting materials were analytical grade. La2O3, EuO3 and (NH4)2HPO4 weighed in appropriated molar ratios and ground in an agate mortar. Then the powder was treated under 1000 degrees C. The crystal phase of La3PO7:Eu3+ was investigated by X-ray diffraction (XRD) using a Cu target radiation resource (lamda = 1.54078 ?) and exhibited prominent peaks accordant with JCPDS standard card (33-0720) of La3PO7 in monoclinic phase. Emission and excitation spectra of La3PO7:Eu3+ were recorded at room temperature using a fluorescence spectrometer (Hitachi F-4500). Under 254 nm excitation, intense red fluorescence was observed from La3PO7:Eu3+, which was assigned to the (5)D0-->(7)F2 transition of Eu3+ ions. The intensity of the (5)D0-->(7)F2 transition is stronger than that of the (5)D0-->(7)F1 transition, showing that the Eu3+ ions were in the non-centrosym-metric sites in La3PO7. The CommissionIn-ternational DeL" Eclairage (CIE) coordinate of La3PO7:Eu3+ is (0.63,0.37) in the red area of CIE1931 XY chromaticity coordinate graph and close to that of Y2o3:Eu3+, but the cost of La3PO7 host is lower. This novel material may have potential applications in plasma display panels and Hg-free fluorescent lamps in the future.

[High efficiency and low threshold upconversion from IR to red for Er3+ and Tm3+ co-doped fluoride-oxide glass-ceramic].

In this paper, high efficiency and low threshold upconversion from IR to red is reported, for Er3+ and Tm3+ co-doped fluoride-oxide glass-ceramic under 978 nm LD excitation. The component of sample in experiment is 65GeO2-25NaF-8.5BaF2-1Er2O3-0.5 Tm2O3, and the prepared method is obtained. The upconversion emission spectra under 978 nm LD excitation is measured at room temperature. Analyzing it, we find that introduction of Tm3+ into Er3+ doped system preferentially quenches the green upconversion fluorescence from 4S3/2 level of Er3+ duo to the efficient cross-relaxation of 4I13/2-->4I15/2 (Er): 3H6-->3H4 (Tm) which can significantly reduce the upconversion efficiency from 4I13/2 level to the emitting 4S3/2 level, and the Tm3+ behaves as a good sensitizer of the red upconversion from the 4F9/2 level of Er3+ which is mainly populated by the cross-relaxation of 3H4-->3H6 (Tm): 4I11/2-->4F9/2 (Er). However, at low Er3+ concentration (2 mol%), it is impossible for strong red upconversion. X-ray analysis is done, there are lots of nanocrystallites in MFG glass-ceramic. So we think, this red upconversion is attributed to Er3+ enriched fluoride microcrystallites, which makes the cross-relaxation of 3H4-->3H6 (Tm): 4I11/2-->4F9/2 (Er) more effective, therefore their active optical properties may be optimised. In the end, the relationship between LD working current and intensity of upconversion luminescence is discussed, the results confirm that both red and green upconversion processes are consisted by two photons.