No abstract

The best performance of the phosphor Li(2)SrSiO(4): Eu(2+), Ce(3+) in terms of luminescence efficiency (LE), color rendering index (CRI) and color temperature (Tc) for light-emitting diode application was optimized with combinatorial approach. The combinatorial libraries were synthesized with solution-based method and the scale-up samples were synthesized with conventional solid-reaction method. Crystal structure was investigated by using the X-ray diffraction spectrometer. The emission spectra of each sample in combinatorial libraries were measured in situ by using a fiber optic spectrometer. Fluorescence spectrometers were used to record excitation and emission spectra of bulk samples. White light generation was tuned up by tailoring Eu(2+) and Ce(3+) concentrations in the single-phased host of Li(2)SrSiO(4) under near-ultraviolet excitation, but it exhibited low efficiency of luminescence and poor color rendering index. The effects of each level of the Eu(2+) and Ce(3+) concentrations on LE, CRI, and Tc were evaluated with the Taguchi method. The optimum levels of the interaction pairs between Eu(2+) and Ce(3+) concentration on LE, CRI, and Tc were [2, 1] (0.006 M, 0.003 M), [1, 2] (0.003 M, 0.006 M), and [3, 1] (0.009 M, 0.00 3M), respectively. The thermal stability of luminescence, the external quantum efficiency (QE), luminance, chromaticity coordinates, correlated color temperature, color purity including the composition ratio of RGB in white light, and color rendering index of the white light emission of phosphor were evaluated comprehensively from a bulk sample.

Anti‐counterfeiting technologies are desired to protect products far away from the violation of dummy, fake and shoddy goods. The phosphor of (Y,Gd)VO4:Bi3+,Eu3+ was synthesized for the application of this purpose. Its photoluminescence was investigated by exciting with different wavelengths at variant temperatures. Wide emission color ranged from green through yellow to orange was tuned up by tailor‐ing Bi3+ and Eu3+ concentrations. The temperature dependent luminescence and wavelength selective excitation of (Y,Gd)VO4:Bi3+,Eu3+ were observed, which provide different encryptions in anti‐counterfeiting. To verify the feasibility in application, two anti‐counterfeiting patterns were fabricated practically and excellent performance was obtained. Moreover, the physical mechanisms for the different phenomena of luminescence were elucidated from excitation spectra combining with the configuration coordinate model. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel phenomenon about the luminescence intensification by the coupling of two phases in a complex was presented. The phosphors were synthesized through solid-state reaction and the highest luminescence was obtained by tailoring SrO and Al 2 O 3 ratios in the SrO-Al 2 O 3 system. The red emission originated from Mn 4þ , while Mn 2þ was also identified from electron paramagnetic resonance spectra. The lattice vibration was observed from Raman spectra. Meanwhile, the dielectric properties were measured. The mechanism based on electromechanical coupling between Sr 4 Al 14 O 25 and SrAl 2 O 4 phases in the 3SrO · 5Al 2 O 3 complex was proposed and discussed from the viewpoint of lattice vibrations and the dielectric field.

No abstract