In this article, we propose a facile method for synthesis of K 2 SiF 6 :Mn 4+ phosphor and discuss its promising application in warm-white light emitting diodes (LED

The processes of extraction and insertion of lithium ions in LiCoO(2) cathode are investigated by galvanostatic cycling and electrochemical impedance spectroscopy (EIS) at different potentials during the first charge/discharge cycle and at different temperatures after 10 charge/discharge cycles. The spectra exhibit three semicircles and a slightly inclined line that appear successively as the frequency decreases. An appropriate equivalent circuit is proposed to fit the experimental EIS data. Based on detailed analysis of the change in kinetic parameters obtained from simulating the experimental EIS data as functions of potential and temperature, the high-frequency, the middle-frequency, and the low-frequency semicircles can be attributed to the migration of the lithium ions through the SEI film, the electronic properties of the material and the charge transfer step, respectively. The slightly inclined line arises from the solid state diffusion process. The electrical conductivity of the layered LiCoO(2) changes dramatically at early delithiation as a result of a polaron-to-metal transition. In an electrolyte solution of 1 mol L(-1) LiPF(6)-EC (ethylene carbonate) :DMC (dimethyl carbonate), the activation energy of the ion jump (which is related to the migration of the lithium ions through the SEI film), the thermal activation energy of the electrical conductivity and the activation energy of the intercalation/deintercalation reaction are 37.7, 39.1 and 69.0 kJ mol(-1), respectively.

High-resolution x-ray photoelectron spectroscopy (XPS) was used to study the chemical nature and physical distribution of N in oxynitride films formed by rapid thermal N2O processes (RTPs). High-resolution synchrotron Si 2p core level photoemission spectroscopy (PES) was used to study the oxide/Si(100) interface suboxide structures with and without the presence of N. XPS N 1s studies indicated that there are two types of N in the RTP oxynitride films. The chemical bond configuration of the first type of N is similar to that N in Si3N4 and is mainly distributed within the first 1 nm from the interface. The second type of N is distributed mainly outside of the first 1 nm region, and the N is likely bonded to two Si and one oxygen atom. PES studies showed that Si formed suboxides with oxygen at the interface for all oxynitride films. It is found that there is no change in the Si+1 structure while there is a dramatic intensity decrease in the Si+2 and Si+3 peaks with the inclusion of N in the oxide. Both the XPS and PES results are explained in terms of a strain reduction as N is incorporated in the film near the interface region, where Si3N4 functions as a buffer layer which reduces the stress caused by the large Si ‘‘lattice’’ mismatch between the bulk Si and the oxide overlayer. About 1/5 of the Si+2 and 1/3 of Si+3 atoms at the SiO2/Si interface has been replaced by the Si3N4 buffer layer at the oxynitride/Si interface.

Superbroad near-to-mid infrared (NIR-MIR) photoluminescence was observed from Bi 5 (AlCl 4 ) 3 at room temperature, spanning the spectral range of about 1000 to 4000 nm. On the basis of structural considerations and dynamic analyses, Bi 5 3+ clusters were identified as the optically active species, inherently differing from the species which is typically believed to be active in NIR-emitting Bi-doped glasses. In comparison to most other NIR-luminescent Bi-doped materials, the MIR-part of the luminescence spectrum is still present at room temperature. Emission intensity and excited state lifetime were found to exhibit abnormal temperature dependence, where the former increases with temperature up to a critical value of about 150 K. This behavior is related to a temperature-dependent overlap between ground state and excited states. The observed stabilization of MIR photoemission at room temperature may be a starting point for the development of Bi-based NIR-MIR light sources with superbroad emission spectrum, where Bi 5 3+ or similar polycationic species act as optical gain medium. (2)

A new type of bismuth doped Ba(2)B(5)O(9)Cl crystal is reported to exhibit broadband near infrared (NIR) photoluminescence at room temperature, which has been identified here originating from elementary bismuth atom. Rietveld refining, static and dynamic spectroscopic properties reveal two types of Bi(0) centers in the doped compound due to the successful substitution for two different nine-coordinated barium lattice sites. These centers can be created only in a reducing condition, and when treated in air and N(2)/H(2) flow in turn, they can be removed and restored reversely. As the dwelling time is prolonged in N(2)/H(2) at high temperature, conversion from Bi(2+) to Bi(0), as reflected by changes of their relative emission intensities, is witnessed in the crystal of Ba(2)B(5)O(9)Cl:Bi. The lifetime of the NIR luminescence was observed in a magnitude of ~30 μs, rather different from bismuth doped either glasses or crystals reported previously.

Transparent glass ceramics containing Ce 3+ -Yb 3+ codoped Y 3 Al 5 O 12 nanocrystals were prepared, and their microstructures were characterized by X-ray diffraction and transmission electron microscopy. Intense near-infrared emission at around 1000 nm, attributed to the 2 F 5/2 / 2 F 7/2 transition of Yb 3+ , was observed upon excitation at 452 nm. Efficient energy transfer from Ce 3+ ions to Yb 3+ ions was confirmed by the luminescence spectrum and fluorescent lifetime measurements; the mechanism was investigated and demonstrated to be a single-photon process rather than a two-photon process.Greatly enhanced near-infrared emission was achieved from the glass ceramics excited by simulated sunlight from 400 to 800 nm compared with that from as-prepared glass. These results demonstrate that the glass ceramics are promising materials for spectral conversion from visible sunlight to nearinfrared emission and may have potential applications as spectral convertors to enhance the photoelectric conversion efficiency of c-Si solar cells.

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