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rietveld refinement and optical properties of SrWO_4:Eu^(3+) powders prepared by the non-hydrolytic sol-gel method

Journal of Rare Earths 2015年第2期33卷 113-128页

作者： P.F.S.Pereira I.C.Nogueira E.Longo E.J.Nassar I.L.V.Rosa L.S.Cavalcante Chemistry Institute University of the State of Sao Paulo Julio de Mesquita Filho-UNESP Francisco DegniAraraquara-SP 14800-900 Brazil LIEC-Chemistry Department Federal University of Sao Carlos Via Washington Luis Km 235Sao Carlos-SP 13565-905 Brazil University of Franca-UNIFRAN Via Dr.Armando Sales de OliveiraNo.201 Franca-SP 14404-600 Brazil CCN-DQ-GERATEC University of the State of Piauí Joao Cabral 2231 P.O.Box 391Terezina PI 64002-150 Brazil

We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 *** and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and rietveld refinement data confirmed that all powders had a scheelite-type tetragonal ***-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]*** properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ *** properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry *** PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.

关键词： SrWO4 rietveld refinement optical band gap Eu^(3+) +-rare earth luminescence

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rietveld refinement of New Solid Solution Al_xSb_ ( 3-x)Y_5 (0≤x≤2.16)

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Journal of Rare Earths 2005年第S1期23卷 427-429页

作者：曾令民林郭强农亮勤梁建烈韦卫星黄开连 Key Laboratory of Nonferrous Metal Materials and New Processing Technology Ministry of Education Guangxi University Nanning 530004 China College of Electronic and Communication Engineering Guangxi University for Nationalities Nanning 530006 China Key Laboratory of Nonferrous Metal Materials and New Processing Technology Ministry of Education Guangxi University Nanning 530004 China College of Electronic and Communication Engineering Guangxi University for Nationalities Nanning 530006 China

The X-ray diffraction analyses show that the existence of a continuous solid solution of Al_xSb_ 3-xY_5 (0≤x≤216). Al_xSb_ 3-xY_5 crystallizes in the hexagonal system with the space group P6_3/mcm (193) and Mn_5Si... 详细信息

关键词： rare earths crystal structure X-ray powder diffraction rietveld refinement

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rietveld refinement of powder X-ray diffraction,microstructural and mechanical studies of magnesium matrix composites processed by high energy ball milling

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Journal of Magnesium and Alloys 2018年第4期6卷 390-398页

作者： T.Ramkumar M.Selvakumar R.Vasanthsankar A.S.Sathishkumar P.Narayanasamy G.Girija Department of Mechanical Engineering Dr.Mahalingam College of Engineering and TechnologyPollachi 642003India Department of Automobile Engineering Dr.Mahalingam College of Engineering and TechnologyPollachi 642003India Department of Mechanical Engineering Sree Sowdambika College of EngineeringAruppukottai 626134India Department of Mechanical Engineering Kamaraj College of Engineering and TechnologyVirudhunagar 626001India

This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy *** of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction *** rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical *** examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium *** results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline *** hardness of the composite samples is calculated by Vickers’s Hardness ***,dry sling wear test and corrosion test are performed for the fabricated *** with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.

关键词： rietveld refinement X-ray diffraction Crystal structure Micro structure Wear and corrosion

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Spectroscopic studies and rietveld refinement of strontium-britholites

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Journal of Rare Earths 2008年第4期26卷 483-489页

作者： Khaled Boughzala Ezzedine Ben Salem Fethi Kooli Pierre Gravereau Khaled Bouzouita U. R. Matériaux Inorganiques Institut Préparatoire aux Etudes d'Ingénieurs Rue Ibn ElJazzr 5019 Monastir Tunisia Department of Chemistry Taibah University P.O.Box 30002. Almadinah Almunawwarah Saudi Arabia 87 Avenue du Dr Schweitzer 33608 Pessac Cedex France

Strontium-britholites whose chemical formula was Sr10-xLax（PO4）6-x（SiO4）xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the rietveld method indicated that La^3＋ ions were located into the two sites with a strong preference for metal （2） sites especially for low contents. A progressive shift of the F position along the c-axis outside the centre of the triangle formed by metal （2）-atoms was observed with the increase of x. The infrared and Raman spectra exhibited the characteristic vibration modes of PO4 and SiO4groups confirming the incorporation of this last group into the apatite structure. The 295i MAS-NMR spectra exhibited one resonance peak confirming the data obtained by X-ray diffraction, indicating that P and Si were located in the same crystallographic site.

关键词： strontium brithofites rietveld refinement infrared spectroscopy nuclear magnetic resonance (NMR) Raman spectroscopy rare earths

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Application of high energy X-ray diffraction and rietveld refinement in layered lithium transition metal oxide cathode materials

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Nano Research 2023年第7期16卷 9954-9967页

作者： Zhuo Yang Yong Lu Xiaomeng Liu Fujun Li Jun Chen Renewable Energy Conversion and Storage Center(RECAST) Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education)College of ChemistryNankai UniversityTianjin 300071China

Layered lithium transition metal oxide(LTMO)cathode materials have attracted much attention for lithium-ion batteries and are shining in the current *** a clear structure-performance relationship is necessary for the performance improvement of LTMO cathode *** combination of synchrotron X-ray diffraction(XRD)with high intensity and XRD rietveld refinement is powerful for revealing the structural characteristics of LTMO cathode *** review summarizes the application of high energy XRD and rietveld refinement in LTMO cathode materials,including the brief introduction of synchrotron XRD and rietveld refinement and their applications in understanding the structural evolution related to the synthetic,thermal runaway,cycling,and high-rate charge/discharge process of LTMO cathode *** XRD can provide insights into the intermediates and reaction paths in the synthesis process,the origin of thermal runaway,the mechanism of structural decay during cycles,and the structural evolution during high-rate charging/*** works should focus on the development of higher intensity X-rays to gain more in-depth insights into the intrinsic relationship between their structural characteristics and properties.

关键词： synchrotron X-ray diffraction rietveld refinement layered cathode materials transition metal oxide lithium-ion batteries

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X-ray diffraction analysis by rietveld refinement of FeAl alloys doped with terbium and its correlation with magnetostriction

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Journal of Rare Earths 2023年第8期41卷 1217-1224,I0004页

作者： J.S.Uribe-Chavira G.Herrera-Pérez C.R.Santillán-Rodríguez R.J.Sáenz-Hernández J.A.Matutes-Aquino M.C.Grijalva-Castillo Materials Physics Department Centro de Investigación en Materiales AvanzadosS.C.Miguel de Cervantes 120Chihuahua31136ChihMexico CONACYT–Centro de Investigación en Materiales Avanzados S.C.Miguel de Cervantes 120Chihuahua31136ChihMexico

Fe_(81)Al_(19) polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc *** introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal *** examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 *** a consequence of doping with Tb,the lattice parameter increases,so the calculated apparent crystallite size increases,indicating a decrease in dislocation density and therefore in *** change in the magnetostriction with the magnetic field,dλ_(T)/dH,is directly related to strain anisotropy that can favor the iron easy magnetization axis on the [100] *** increase in total magnetostriction is found in the doped alloys with a maximum of 90 × 10^(-6) at 300 K for the alloy containing 0.027 at% *** enhancement is a threefold value of the undoped alloy,which is attributed to the smaller maximum strain value and the preferential orientation formation by the columnar grains.

关键词： FeAl alloy Magnetostriction rietveld refinement Microstrains Preferred orientation Rare earths

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Structural analysis by rietveld refinement of calcium and lanthanum phosphosilicate apatites

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Journal of Rare Earths 2013年第9期31卷 897-904页

作者： Hela Njema Khaled Boughzala Habib Boughzala Khaled Bouzouita Laboratory of Industrial Chemistry National School of Engineering of Sfax Preparatory Institute for Engineering Studies of Monastir Laboratory of Materials and Crystallochemistry Preparatory Institute for Engineering Studies of Nabeul

Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.

关键词： britholites rietveld refinement infrared spectroscopy charge distribution method rare earths

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rietveld structure refinement of microcline

Rietveld structure refinement of microcline

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中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： SHANKE LIU Key Laboratory of Mineral Resources Institute of Geology and GeophysicsChinese Academy of Sciences

Compared with single-crystal X-ray diffraction,extracting structural data from X-ray powder diffraction(XRPD)seems meaningless for minerals with an available single crystal,such as alkali ***,alkali feldspar is highly abundant on Earth,and the feldspar structure is important in ***,the potential of extracting structural parameters from powder diffraction data collected using conventional Bragg-Brentano XRPD(BB-XRPD)with CuKαradiation is worthy of ***-XRPD may be the most extensively used instrument in the laboratory and has a major advantage in terms of cost and ***,by combining the rietveld method with the General Structure Analysis System(GSAS)of BB-XRPD,a microcline structure in a natural feldspar sample with two minor impurities was refined for the first *** extract high-quality structural data,a formula related to Si/Al-O bond lengths and Si/Al occupancies in terms of the crystal structure database and a new model are sequentially *** reliability of the structural data for such a low-symmetry phase as microcline is discussed and established by comparison with published single-crystal data.

关键词： microcline feldspar crystal structure rietveld refinement X-ray powder diffraction

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Analysis of the new ternary phase with C_(6)Cr_(23) structure in Mg-Co-B system by rietveld method and physical properties of its Ni-substituting effect

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Journal of Magnesium and Alloys 2022年第7期10卷 1899-1908页

作者： Qiang Feng Changzhong Liao Cheng Dong Kaimin Shih Minhua Su College of Physics and Engineering Chengdu Normal UniversityChengduSichuan 611130China Department of Civil Engineering The University of Hong KongHong KongChina National Laboratory for Superconductivity Institute of Physics and Beijing National Laboratory for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100190China Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources School of Environmental Science and EngineeringGuangzhou UniversityGuangzhou 510006China

A new ternary Mg_(1.4)Co_(21.6)B_(6) compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure,thermal stability,solid solubility and physical properties were systematically *** crystal structure of the Mg_(1.4)Co_(21.6)B_(6) compound was fully determined by the X-ray diffraction technique with rietveld refinement *** is found that Mg_(1.4)Co_(21.6)B_(6) crystallizes in the form of C_(6)Cr_(23) structure type(space group:Fm-3m(No.225),a=10.5617(2)A,Z=4).The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M_(2-x)Ni_(21+x)B_(6) form belonging to the W_(2)Cr_(21)C_(6)-*** Mg_(1.4)Co_(21.6)B_(6) is repeatedly sintered at elevated temperatures,it becomes unstable and decomposes into Co3B and *** lattice parameters of the Mg_(1.4)Co_(21.6)B_(6) solid solution alters dramtically with increasing Ni substitution,with no regular trend being *** electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B(nominal compositions)samples suggest that both samples are typical ferromagnetic *** temperature in the maximum drop of theρ(T)curve decreases as a function of the Ni *** on the correlation between the critical temperature and Ni content,a linear fitting equation is obtained and the critical temperature of Mg_(1.4)Co_(21.6)B_(6) calculated utilizing the linear fitting *** findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.

关键词： Mg-Co-Bsystem Crystal structure Stability Ni-substituting effect rietveld refinement

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The role of defects association in structural and transport properties of the Ce_(1-x)(Nd_(0.74)Tm_(0.26))_xO_(2-x/2) system

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Journal of Energy Chemistry 2021年第9期30卷 494-502页

作者： Cristina Artini Sabrina Presto Massimo Viviani Sara Massardo Maria Maddalena Carnasciali Lara Gigli Marcella Pani DCCI Department of Chemistry and Industrial ChemistryUniversity of GenovaVia Dodecaneso 3116146 GenovaItaly Institute of Condensed Matter Chemistry and Technologies for Energy National Research CouncilCNR-ICMATEVia De Marini 616149 GenovaItaly Institute of Condensed Matter Chemistry and Technologies for Energy National Research CouncilCNR-ICMATEc/o DICCA-UNIGEVia all’Opera Pia 1516145 GenovaItaly INSTM Genova Research UnitVia Dodecaneso 3116146 GenovaItaly Elettra-Sincrotrone Trieste S.C.p.A. ss 14km 163.534149 BasovizzaTriesteItaly CNR-SPIN Genova Corso Perrone 2416152 GenovaItaly

An experimental investigation of the crystallographic,Raman and transport properties of the Ce_(1-x)(Nd_(0.74)Tm_(0.26))_xO_(2-x/2)(0.1≤x≤0.6) doped ceria system was performed with the aim of setting out correlations between structural features and ionic conductivity of the *** chosen composition ensures that the average size of the Nd^(3+) and Tm^(3+) doping ions coincides with the one of Sm^(3+);even so,the studied system presents larger cell parameters and a wider compositional extent of the CeO_(2)-based solid solution than Sm-doped ***,the occurrence of two different activation energies to ionic conduction below and above ~750 K determines the existence of two distinct conduction *** described experimental results agree with the formation below the threshold temperature of1 V_O2 Tm'_(Ce) trimers,which promote the incorporation of Nd'_(Ce) isolated defects into the CeO_(2)-based solid *** the high temperature range the dissociation of trimers induces the appearance of a lower activation energy;the extrapolation of its value at infinite dilution provides a result in good accordance with the expected binding energy of 1 V_ORE'_(Ce) dimers,pointing at their stability even in the high temperature conduction regime.

关键词： Solid oxide fuel cells RE-doped ceria High resolution X-ray powder diffraction rietveld refinement μ-Raman spectroscopy Impedance spectroscopy

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