Zhixiong Zhang

Luminescent properties of Ce3+/Tb3+co-doped glass ceramics containing YPO4 nanocrystals for W-LEDs

Abstract Ce 3+ /Tb 3+ co-doped transparent glass ceramics containing YPO 4 nanocrystals were prepared using high temperature melting method, and their structural and luminous properties were investigated. XRD analysis and TEM images confirmed the existence of YPO 4 nanocrystals in glass ceramics. The transmission spectra proved that the glass ceramics specimens still maintained a high transparency. Then the excitation and emission spectra of the Ce 3+ and Tb 3+ single-doped and co-doped glass and glass ceramics were discussed, which proved that the glass ceramics had better luminescent properties. Under the near ultraviolet (331 nm) excitation, the broadband emission located at 385 nm was observed which was ascribed to 5d→ 2 F 5/2 and 2 F 7/2 transition of Ce 3+ ions. Several characteristic sharp peaks centered at 489, 543, 578 and 620 nm originated from the 5 D 4 to 7 F J ( J =6, 5, 4, 3) of Tb 3+ ions. The decay time of Tb 3+ ions at 543 nm and the relevant energy levels of Ce 3+ ions and Tb 3+ ions illustrated the transfer process from Ce 3+ ions to Tb 3+ ions. The best CIE chromaticity coordinate of the glass ceramics specimen was calculated as ( x =0.3201, y =0.3749), which was close to the NTSC standard values for white ( x =0.333, y =0.333). All the results suggested that the YPO 4 -based Ce 3+ /Tb 3+ co-doped glass ceramics could act as potential luminescent materials for white light-emitting diodes.

Luminescent properties of Eu2+-doped BaGdF5 glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

Eu2+ doped transparent oxyfluoride glass ceramics containing BaGdF5 nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd3+ ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu2+ doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd3+ to Eu2+ ions, the energy transfer efficiency from Gd3+ to Eu2+ ions was discussed. In a...

Enhanced magnetostrictive effect in epoxy-bonded TbxDy0.9-xNd0.1(Fe0.8Co0.2)(1.93) pseudo 1-3 particulate composites

The spin configuration and spontaneous magnetostriction λ111 of TbxDy0.9−xNd0.1(Fe0.8Co0.2)1.93 (0.20 ≤ x ≤ 0.60) alloys have been investigated. The easy magnetization direction (EMD) at room temperature was observed towards the 〈111〉 axis when 0.40 ≤ x ≤ 0.60, accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients λ111, which increases from 1640 ppm for x = 0.40 to 1900 ppm for x = 0.60. The strong 〈111〉-oriented pseudo 1–3 particulate composite was fabricated by embedding and aligning particles in a passive epoxy matrix under an applied magnetic field. An enhanced magnetostrictive effect, the large low-field magnetostriction, λa, as high as 480 ppm at 3 kOe, was obtained for the sample of x = 0.40, in an excess of 75% of its polycrystalline alloy although it only contains 27 vol. % alloy particles. This enhanced effect can be attributed to its low magnetic anisotropy, anisotropic magnetostrictive nature (e.g., λ111 ≠ λ100, 〈111〉EMD), chain structure, and the 〈111〉-...