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Chinese Physics Letters 2004年第4期21卷 737-740页

作者：李山东毕红方江邻钟伟都有为 NationalLaboratoryofSolidStateMicrostructureandDepartmentofPhysics NanjingUniversityNanjing210093 CollegeofChemistryandChemicalEngineering AnhuiUniversityHe/e/230039 CenterforMaterialsAnalysis NanjingUniversityNanjing210093

We prepare two kinds of Co3O4 antiferromagnetic nanocrystallite systems with different surface structures: one grain surface is covered by polymer decomposition residues (PDRs) (referred to as CS) and the other is naked (NS). It has been found that the magnetic properties of the CS sample deviate greatly from those of the NS sample. For example, the CS sample exhibits an open loop up to 8T at 4.2K, while the two branches of the hysteresis loop for the NS sample superpose together when the field is in excess of 3T. The average permanent magnetic moments per Co3O4 cell for the CS sample are about three times larger than that of the NS sample. The coercivity and loop shift for the CS sample are enhanced remarkably in comparison with the NS sample, i.e., from 73.8 and 11.0kA/m for the NS sample to 116.5 and 25.5kA/m for the CS sample, respectively. The anomalous magnetic properties and their enhancements for the CS sample are attributed to the surface spin pinning effect by PDRs.

关键词： nanocrystallites

Cathodoluminescent properties of Tb^(3+)-doped yttria nanocrystallites

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Journal of Rare Earths 2009年第4期27卷 574-578页

作者： P.Psuja D.Hreniak W.Strek Institute of Low Temperature and Structure Research Polish Academy of Sciences ul.Okolna 2 50-422 Wroclaw Poland

The Tb3＋-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystaUites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr：Al2O3 was mixed with Th3＋：Y2O3 powders and its normalized emission was used. to measure a relative intensity of Tb3＋：Y2O3. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.

关键词： cathodoluminescence yttria phosphors nanocrystallites Tb^3＋ rare earths

Influence of concentration and sintering temperature on luminescence properties of Eu^(3+):SnO_2 nanocrystallites

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Journal of Rare Earths 2012年第7期30卷 627-631页

作者： P. Psuja W. Strek Institute of Low Temperature and Structure Research of Polish Academy of Sciences

The nanopowders of SnO2 doped with different Eu^3＋ concentrations were synthesized using the modified Pechini method. The Eu^3＋ concentrations were high above solubility limit. The average size of crystallites was controlled by the sintering temperatures. The structure and the morphology of obtained powders were examined using the XRD （X-ray diffraction） and TEM （transmission electron microscopy） analyses. The Eu2Sn2O7 phase separation was observed at relatively high concentration of Eu^3＋ ions. The ZnS：Ag micropowders were mixed with the Eu^3＋：SnO2 powders and their normalized emission was used to measure a relative efficiency of Eu3＋：SnO〉 The photoluminescence spectra of mixed powders were measured in function of Eu^3＋ concentration and average size of nanocrystallites. The reference peak method was used for comparison of intensities of the samples and selection of optimal one. The influence of the average grain size and Eu^3＋ concentration on the phosphor＇s efficiency was discussed. The presented results confirmed the rightness of synthesis of the Eu^3＋：SnO2 in form of nanocrystalites with relatively high Eu^3＋ concentration.

关键词： SnO2 nanocrystallites Eu^3＋ luminescence phosphors rare earths

Hydrothermal Synthesis and Characterization of Europium-doped Barium Titanate nanocrystallites

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Nano-Micro Letters 2013年第1期5卷 57-65页

作者： Margarita García-Hernndez Geneviève Chadeyron Damien Boyer Antonieta García-Murillo Felipe Carrillo-Romo Rachid Mahiou Universidad Autónoma Metropolitana Departamento de Ciencias NaturalesDCNIUnidad CuajimalpaPedro Antonio de los Santos 8411850 Mxico D.F. Mxico Clermont Universit Institut de Chimie de Clermont-Ferrand UMR 6296CNRS/UBP/ENSCCFBP 10448F-63000 Clermont-Ferrand Instituto Politcnico Nacional CIITEC IPNCerrada de Cecati S/N. Col. Santa CatarinaAzcapotzalco Mxico D.F. C.P. 02250Mxico

Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO_3 consisting of spherical particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900 was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu^(3+)was used as a structural probe, and the luminescence properties recorded from Ba TiO_3 :Eu^(3+)and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles.

关键词： BaTiO3 Europium nanocrystallites Hydrothermal technique

Visible Light Induced Photocatalysis of Cerium Ion Modified Titania Sol and nanocrystallites

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Journal of Materials Science & Technology 2004年第1期20卷 14-18页

作者： Yibing XIE and Chunwei YUANKey Laboratory of Molecular & Biomolecular Electronics, Southeast University, Ministry of Education, Nanjing 210096, China Southeast Univ Key Lab Mol & Biomol Elect Minist Educ Nanjing 210096 Peoples R China

The cerium ion(Ce4+) doped titania sol and nanocrystallites were prepared by chemical coprecipitation-peptization and hydrothermal synthesis methods, respectively. The X-ray diffraction pattern shows that Ce4+-TiO2 xerogel powder has semicrystalline structure and thermal sintering sample has crystalline structure. Ce4+-TiO2 nanocrystallites are composed of the major anatase phase titania (88.82 wt pct) and a small amount of crystalline cerium titanate. AFM micrograph shows that primary particle size of well-dispersed ultrafine sol particles is below 15 nm in diameter. The particle sizes are 30 nm for xerogel sample and 70 nm for nanocrystallites sample, which is different from the estimated values (2.41 nm and 4.53 nm) by XRD Scherrer's formula. The difference is mainly due to aggregation of nanocrystallites. The experimental results exhibit that photocatalysts of Ce4+-TiO2 sol and nanocrystallites have the ability to photodegrade reactive brilliant red dye (X-3B ) under visible light irradiation with the ion-TiO2/VIS/dye system. Moreover, Ce4+ doped titania sol has shown higher efficiency than the nanocrystallites sample in respect of potocatalytic activity. Meanwhile, dye photodegradation mechanisms are proposed to different photocatalytic reaction systems, which are dye photosensitization, ion-dye photosensitization and interband photocatalysis & dye photosensitization with respect to TiO2 nanocrystallites, Ce4+-TiO2 sol and Ce4+-TiO2 nanocrystallites system.

关键词： Photocatalytic activity Sol nanocrystallites Photosensitization Reaction mechanism

NEW ISOTHERMAL MODEL FOR GRAIN GROWTH IN nanocrystallites

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化工学报 2004年第7期55卷 1206-1207页

作者：屈一新宋晓岚 College of Chemical Engineering Beijing University of Chemical Technology Beijing 100029 China School of Resources Processing and Bioengineering Central South UniversityChangsha 410083HunanChina

INTRODUCTION nanocrystallites with an average grain size of less than 100 nm have attracted considerable scientific interest because of the improvements in a variety of properties resulted from grain-size refinement in the nanometer scale.The investigation of the thermal stability or grain growth behavior is therefore important from the technological point of view as well as for the purpose of scientific study.

关键词： grain growth nanocrystallites model

Preparation and 1.06μm Fluorescence Decay of Nd3+-Doped Glass Ceramics Containing NaYF4 nanocrystallites

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Chinese Physics Letters 2019年第8期36卷 51-55页

作者：黄兴勇陈大钦沈必舟宋海智 Southwest Institute of Technical Physics Chengdu610041 School of Physics and Electronic Engineering Yibin UniversityYibin644007 College of Physics and Energy and Fujian Provincial Key Laboratory of Quantum Manipulation and New EnergyMaterialsFujian Normal UniversityFuzhou350117 ENREACH Education(ChengDu)of Dipont Education Management Group Chengdu617000 Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu610054

Considered to be a candidate for large-size bulk materials used in lasers and other fields,Nd3+-doped glass ceramics containing NaYF4 nanocrystallites are prepared.Using x-ray diffraction and transmission electron microscopy,we show that pure cubic NaYF4 is well precipitated in the glass matrix.To obtain the optical property of this material at 1.06 μm,the fluorescence decay of 4F3/2 energy levels is measured and analyzed.It is found that the fluorescence lifetime decreases first and then increases with the increasing dopant concentration due to the existing but finally weakening energy dissipation.As a result,a long radiation lifetime of about 191-444μs is obtained at 1.06μm in the prepared material.It is thus revealed that Nd3+-doped glass ceramic containing NaYF4 nanocrystallites is a potential candidate as a near-infrared laser material.

关键词： nanocrystallites Preparation Fluorescence

Production and characterization of ZnO nanoparticles and porous particles by ultrasonic spray pyrolysis using a zinc nitrate precursor

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International Journal of Minerals,Metallurgy and Materials 2012年第7期19卷 651-656页

作者： Burak Ebin Elif Arτg Burak zkal Sebahattin Gürmen Metallurgical & Materials Engineering Department Istanbul Technical University

ZnO nanoparticles and porous particles were produced by an ultrasonic spray pyrolysis method using a zinc nitrate precursor at various temperatures under air atmosphere. The effects of reaction temperature on the size and morphology of ZnO particles were investi- gated. The samples were characterized by energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. ZnO particles were obtained in a hexagonal crystal structure and the crystallite shapes changed from spherical to hex- agonal by elevating the reaction temperature. The crystallite size grew by increasing the temperature, in spite of reducing the residence time in the heated zone. ZnO nanoparticles were obtained at the lowest reaction temperature and ZnO porous particles, formed by aggregation of ZnO nanoparticles due to effective sintering, were prepared at higher temperatures. The results showed that the properties of ZnO particles can be controlled by changing the reaction temperature in the ultrasonic spray pyrolysis method.

关键词： zinc oxide nanoparticles nanocrystallites porous materials ultrasonic applications spray pyrolysis

Synthesis and optical properties of Eu^(3+) ion doped nanocrystalline hydroxya patites embedded in PMMA matrix

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Journal of Rare Earths 2011年第12期29卷 1111-1116页

作者： R.J.Wiglusz A.Bednarkiewicz W.Strek Institute of Low Temperature and Structure Research Polish Academy of Sciences

Transparent, luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications. Transparent polymethyl methacrylate （PMMA） polymer nanocornposites modified with thenoyl- trifluoroacetonate （TAA） were fabricated by in situ polymerization and used as hosts for homogenous dispersion of 3 mol.% Eu^3＋：Ca10（PO4）6（OH）2 （Eu^3＋：HA） hydroxyapatite -20 nm large nanocrystals. The emission, excitation and transmission spectra as well as the fluorescence decay rates of bare Eu^3＋：HA nanocrystallites, Eu^3＋：HA embedded in the PMMA and and Eu：HA embedded in the PMMA/TTA rtanocomposites were studied. The improvement of transparency was demonstrated with the addition of TTA as well as europium doped hydroxyapatites in comparison to pure PMMA matrix. The Judd-Ofelt analysis of f-f transitions of Eu^3＋：HA nanocrystallites, the PMMA/Eu^3＋：HA and the PMMA＋TTA/Eu^3＋：HA was performed to investigate the optical behavior of the polymeric composites.

关键词： photoluminescence hydroxyapatites Eu^3＋ doping nanocrystallites nanocomposites PMMA Judd-Ofelt analysis rare earths

An impact of sintering temperature and doping level on structural and spectral properties of Eu-doped strontium aluminium oxide

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Journal of Rare Earths 2011年第12期29卷 1105-1110页

作者： R.J.Wiglusz T.Grzyb A.Watras P.J.Deren S.Lis W.Strek Institute for Low Temperature and Structure Research Polish Academy of Sciences Department of Rare Earths Adam Mickiewicz University

In the present work, a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3＋ions. The raw nano- materials were thermally treated at 900 to 1100℃ for 3 h. The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion. Our studies were focused on relating the luminescence properties of the Eu^3＋ dopant to the NC （nanocrystallites） size. This was achieved by varying the calcinations temperature between 900 and 1100 ℃. The average NC size varied accordingly between -36 and -75 nm. We found that size effect manifested mainly in the expansion of the cell volume and broadening of XRD peaks as indicated by Rietveld analysis. Moreover the emission and excitation spectra, although typical for Eu^3＋ ions, demonstrated some degree of variability with calcinations temperature and doping concentration. To explain these differences a detailed analysis of luminescence spectra by the Judd-Ofelt theory was performed.

关键词： photoluminescence SrAl2O4 spinel powders Eu^3＋ doping nanocrystallites sol-gel method rietveld analysis Judd-Ofelt theory rare earths