The Luminescence Properties of ZnO:Al Nanopowders Obtained by Sol-gel, Plasma and Vaporization-Condensation Methods

2007 ◽  
Vol 128 ◽  
pp. 135-140 ◽  
Author(s):  
Larisa Grigorjeva ◽  
Donats Millers ◽  
Krishjanis Smits ◽  
Claude J.A. Monty ◽  
Jules Kouam ◽  
...  
Keyword(s):  
Vapour Deposition ◽  
Sol Gel ◽  
Deposition Process ◽  
Raw Material ◽  
Blue Luminescence ◽  
Luminescence Properties ◽  
Luminescence Spectra ◽  
Decay Kinetics ◽  
Zno Nanocrystals ◽  
Pulse Density

ZnO nanocrystals were synthesized and characterized by XRD and SEM methods. The luminescence spectra and decay kinetics were studied under pulsed laser excitation (266 nm, 8 ns). ZnO and ZnO:Al powders were prepared by sol-gel and plasma chemical synthesis. These powders were used as a raw material for the SPVD (Solar Physical Vapour Deposition) process. In this way, the vaporisation-condensation phenomenon (VC) led to the formation of ZnO whiskers and nanopowders. The luminescence properties of the VC nanopowders were studied and compared to those displayed by the raw material. The Al dopant, present in the raw powders as a solid solution and ZnAl2O4 precipitates, was only present as Al ions in the nanopowders after the SPVD. The blue luminescence intensity increased considerably after SPVD. The whiskers type microstructures showed nonlinear blue luminescence dependent on the excitation pulse density.

Luminescence Properties of Ytterbium Activated PLZT Ceramics

2016 ◽  
Vol 98 ◽  
pp. 64-69
Author(s):  
Malgorzata Plonska ◽  
Wojciech A. Pisarski ◽  
Joanna Pisarska
Keyword(s):  
Near Infrared ◽  
Sol Gel ◽  
Ceramic Matrix ◽  
Luminescence Decay ◽  
Luminescence Properties ◽  
Luminescence Spectra ◽  
Activator Concentration ◽  
Ceramic Powders ◽  
Co Doping ◽  
Infrared Luminescence

In the present work the influence of co-doping with ytterbium ions (for 0, 0.5, 1.5, 2.5 wt.% of Yb3+) on physical properties of 8/65/35 PLZT was studied. The ceramic powders were synthesized by the modified sol-gel method, and underwent consolidation by the pressure-less sintering techniques, in Ts=1200°C/6h. Our investigations give a detailed account of the relationships between concentrations of trivalent ytterbium ions in PLZT matrix, on their structure, microstructure, as well as luminescence properties. Near-infrared luminescence spectra at about 1020 nm were registered, which correspond to 2F5/2 - 2F7/2 transition of Yb3+. Based on decay measurements, the luminescence lifetimes for the 2F5/2 excited state of Yb3+ were determined. Luminescence decay analysis indicates that the 2F5/2 lifetime increase with increasing activator concentration (Yb3+) in PLZT ceramic matrix.

Synthesis and Luminescence Properties of YVO4:Eu 3+ Nanocrystals by a Sol-Gel Method

2013 ◽  
Vol 634-638 ◽  
pp. 2268-2271 ◽  
Author(s):  
Yan Hong Li ◽  
Guo Feng Zang ◽  
Jing Ma
Keyword(s):  
Charge Transfer Band ◽  
Sol Gel ◽  
Emission Spectra ◽  
Heat Treating ◽  
Luminescence Properties ◽  
Luminescence Spectra ◽  
Complexing Agent ◽  
Gel Method ◽  
Sol Gel Method ◽  
Crystallite Sizes

YVO4:Eu3+ nanocrystals were synthesized using a sol-gel method which citric acid was used as complexing agent and ethylene glycol was used as coupler. In order to study the influence of heat treating temperature and time on structure and luminescence properties of YVO4:Eu3 nanocrystals, the dry gels were heated at 400 oC, 500 oC and 600 oC for 1 h, 600 o C for 3 h, respectively. X-ray diffraction, SEM and luminescence spectra were used to characterize the structure and luminescence properties. The results of XRD indicate that YVO4:Eu3+ nanocrystals with tetragonal zircon were obtained. The average crystallite sizes of the samples increase with the increasing heat treating temperatures. The results of excitation and emission spectra show that the broad excitation band is assigned to charge transfer band of Eu-O and V-O, the emissions peaks are from 5D0-7FJ transitions. The emission intensities increase with increasing heat treating temperature and time. The local environments of Eu3+ ions in the samples prepared at different conditions are discussed.

The Microwave-Assisted Preparation and Properties of SiO2 Aerogels by Fractional Modification

2010 ◽  
Vol 148-149 ◽  
pp. 1152-1162 ◽  
Author(s):  
Wen Zhi Zheng ◽  
Li Chen ◽  
Xiang Hua Huang ◽  
Lei Fu
Keyword(s):  
Ambient Pressure ◽  
Sol Gel ◽  
Ambient Pressure Drying ◽  
Base Catalysis ◽  
Raw Material ◽  
Microwave Method ◽  
Scanning Calorimetry ◽  
Hydrophobic Sio2 ◽  
Water Bath Heating ◽  
Fractional Modification

Under microwave radiation and using trimethyl chlorosilane as modifier, hydrophobic SiO2 aerogel was prepared through fractional hydrophobic modification and ambient pressure drying of the raw material, tetraethoxysilane (TEOS), in the process of sol-gel and acid-base catalysis. Hydrophilic SiO2 aerogels were also prepared using the microwave method and water bath heating method. The SiO2 aerogels prepared using the three methods, including their morphology and chemical composition, were analyzed and compared using scanning electron microscopy, Brunauer-Emmett-Teller analysis method, Fourier transform infrared spectroscopy, X-ray diffraction, and themogravimetric-differential scanning calorimetry. The results indicate that by adopting the microwave reaction, the specific surface area of the SiO2 aerogels was effectively increased and the structure of the internal nanoscale pores of petal-coated shape was found to exist under the dense external surface of the SiO2 aerogels. Thermal stability of the hydrophobic SiO2 aerogels prepared through fractional modification assisted by the microwave method was increased with the hydrophobic angle at153°, which showed super hydrophobicity.

Synthesis and luminescence properties of Y2O2S:Dy3+, Mg2+, Ti4+phosphors prepared by sol–gel process

2014 ◽  
Vol 40 (2) ◽  
pp. 2663-2668 ◽  
Author(s):  
Ping Huang ◽  
Xueqin He ◽  
Cai’e Cui ◽  
Lei Wang
Keyword(s):  
Sol Gel ◽  
Luminescence Properties ◽  
Sol Gel Process
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