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Academic literature on the topic 'Rietveld method'

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Journal articles on the topic "Rietveld method"

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Rietveld, Hugo M. "The Rietveld method." Physica Scripta 89, no. 9 (August 1, 2014): 098002. http://dx.doi.org/10.1088/0031-8949/89/9/098002.

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Sleight, A. W. "The Rietveld method." Materials Research Bulletin 29, no. 6 (June 1994): 695. http://dx.doi.org/10.1016/0025-5408(94)90128-7.

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Dünkel, L. "The Rietveld Method." Zeitschrift für Physikalische Chemie 196, Part_2 (January 1996): 280–81. http://dx.doi.org/10.1524/zpch.1996.196.part_2.280.

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Rietveld, H. M. "The Rietveld Method: A Retrospection." Zeitschrift für Kristallographie 225, no. 12 (December 2010): 545–47. http://dx.doi.org/10.1524/zkri.2010.1356.

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Oishi-Tomiyasu, R., M. Yonemura, T. Morishima, A. Hoshikawa, S. Torii, T. Ishigaki, and T. Kamiyama. "Application of matrix decomposition algorithms for singular matrices to the Pawley method inZ-Rietveld." Journal of Applied Crystallography 45, no. 2 (March 15, 2012): 299–308. http://dx.doi.org/10.1107/s0021889812003998.

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Z-Rietveldis a program suite for Rietveld analysis and the Pawley method; it was developed for analyses of powder diffraction data in the Materials and Life Science Facility of the Japan Proton Accelerator Research Complex. Improvements have been made to the nonlinear least-squares algorithms ofZ-Rietveldso that it can deal with singular matrices and intensity non-negativity constraints. Owing to these improvements,Z-Rietveldsuccessfully executes the Pawley method without requiring any constraints on the integrated intensities, even in the case of severely or exactly overlapping peaks. In this paper, details of these improvements are presented and their advantages discussed. A new approach to estimate the number of independent reflections contained in a powder pattern is introduced, and the concept of good reflections proposed by Sivia [J. Appl. Cryst.(2000),33, 1295–1301] is shown to be explained by the presence of intensity non-negativity constraints, not the intensity linear constraints.
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Wiessner, Manfred, and Paul Angerer. "Bayesian approach applied to the Rietveld method." Journal of Applied Crystallography 47, no. 6 (October 17, 2014): 1819–25. http://dx.doi.org/10.1107/s1600576714020196.

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The application of the Rietveld method for lattice constant and crystal structure refinement has been undertaken with great success. More routinely, this method is used to estimate quantitative phase amounts and to get information on the coherent diffracting length and the lattice defect density. In this paper an innovative combination of the Rietveld method with the Bayes approach is presented, to obtain directly the distribution of the refined parameters from a measured diffractogram, while the conventional Rietveld technique enables only the deduction of the most probable parameter and the estimation of its precision by confidence intervals. Furthermore, the goal of this work is to promote the development of a robust and automatable Rietveld algorithm. A detailed description of the modified algorithm is presented. Such a modified Rietveld approach is applied to anin situhigh-temperature experiment on a steel sample, including the temperature-dependent α → γ phase transformation reaction during heating and the martensitic transformation during the cooling phase.
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Balić-Žunić, T. "Quantitative powder diffraction phase analysis with a combination of the Rietveld method and the addition method." Powder Diffraction 17, no. 4 (December 2002): 287–89. http://dx.doi.org/10.1154/1.1523872.

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The Rietveld method can be combined with the addition method to determine the absolute quantities of the phases treated by Rietveld refinement plus the quantity of phase(s) not treated by it (amorphous or unobserved). If q is the added proportion of a defined phase already present in the sample, and a1 and a2 its relative proportions as determined by Rietveld refinement prior and after the addition, the proportion of the amorphous (untreated) phase(s) in the original sample is calculated as xo=[a2−(1−q)a1−q]/(1−q)(a2−a1). The absolute quantities of the phases treated by Rietveld refinement are then determined by a correction for the content of the amorphous phase(s), or they can be calculated directly from specific equations. The advantage of the method is that no new variables are introduced in the refinement when the added standard already is a part of the original mixture.
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Schneider, J. "Rietveld method runs on IBM-AT." Acta Crystallographica Section A Foundations of Crystallography 43, a1 (August 12, 1987): C295. http://dx.doi.org/10.1107/s0108767387077535.

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Mitra, G. B., and P. Das Gupta. "The Rietveld method – an alternative approach." Acta Crystallographica Section A Foundations of Crystallography 43, a1 (August 12, 1987): C236. http://dx.doi.org/10.1107/s0108767387079170.

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Rietveld, HM. "The Rietveld Method ? A Historical Perspective." Australian Journal of Physics 41, no. 2 (1988): 113. http://dx.doi.org/10.1071/ph880113.

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differences between observed and calculated values was already well established in crystallography. From there it was, in retrospect, only a small step to refrain from using the integrated intensities as observed values but to use the actual measured profile intensities obtained by step scanning the powder diagram. The Rietveld method was first reported at the I.U.Cr. congress in Moscow in 1966. However, it was not until 1975, when it was also applied to X-ray diffraction, that it became widely accepted. Nowadays its use is no longer confined to elastic neutron powder diffraction, but to all diffraction techniques producing complex diffraction diagrams.
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Dissertations / Theses on the topic "Rietveld method"

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Martins, Murillo Longo [UNESP]. "Síntese e caracterização de ferritas de manganês e zinco visando aplicação como agente de contraste em diagnóstico médico (biosusceptometria de corrente alternada)." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/99701.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Para o aprimoramento de técnicas de diagnóstico e tratamentos de doenças o desenvolvimento de materiais magnéticos é de primordial importância. Neste trabalho as ferritas de manganês e zindo de fórmula geral Mn(1-x)ZNxFe204, onde x assume os valores entre 0,15 e 0,30, foram preparadas pelo método dos precursores poliméricos e caracterizadas por: análises térmicas (termogravimetria associada com análise térmica diferencial (TG/DTA), análise composicional semi-quantitativa por energia dispersiva de raios X (EDX), difratometria de raios X (DRX), refinamento estrutural (Método de Rietveld), adsorção de N2 a 77K (BET), microscopia eletrônica de varredura (MEV), microscopia óptica, espectroscopia de absorção atômica (testes de lixiviação) e medidas de susceptibilidade e permeabilidade magnética. As amostras de ferritas foram também revestidas com quitosana e analisadas com algumas dessas técnicas. Os materiais foram desenvolvidos com o objetivo de utilizá-los como rastreador em biosusceptometria de corrente alternada(BAC), um método de diagnóstico. O método de síntese empregado proporcionou materiais monofásicos em ferrita com baixa porosidade e área superficial. Os materiais apresentaram baixa lixiviação de metais em soluções que simulam os meios fisiológicos do trato gastrointestinal. O revestimento com quitosana foi eficiente suprimindo a dissolução de metais em meios com pHs 7,5 e 6,8. Em pH 1,2, o revestimento se mostrou menos eficiente, porém, ainda assim foi capaz de reduzir a dissolução das espécies que constituem a ferrita. Quanto ao comportamento magnético, as amostras apresentaram magnetizações satisfatórias em 10K e em temperatura ambiente. A amostra contendo zinco a x=0,15 apresentou a mais alta saturação magnética em temperatura ambiente e foi utilizada em um teste com a técnica de BAC apresentando resultados satisfatórios
The development of magnetic materials is of primary importance for the improvement of diagnostic techniques and treatments of diseases. In this work, the manganese and zinc ferrites with general formula of Mn(1-x)ZNxFe204 and 0,15< x <0,30, was prepared by polymeric precursor method and characterized by the physical techniques as: thermal analysis [thermogravimetry and differential thermal analysis (TG/DTA)], ssemi-quantitative analysis of the composition by energy dispersive X ray (EDX), X ray diffractometry (XRD), structural refinement (Rietveld Method), N2 adsorption analysis at 77k (BET), scanning electron microscopy (SEM), optical microscopy, atomic absorption spectroscopy (lixiviation test) and magnetic susceptibility measurements. Chitosan coated samples were also prepared which were analyzed by some of those technique. The materials were developed to be used as a tracer in the alternating current biosusceptometry (ACB), a diagnostic method. The employed synthesis method provided monophasic samples of ferrites with low porosity and surface area. The materials showed low metal solubility in the media that simulate gastrointestinal tract solutions. The chitosan coating was efficient to suppress the metal dissolution in solutions with pHs 7.5 and 6.8. In pH=1.2 medium, the coating was not efficient, but still reduced the resolution of ferrite components. The magnetic measurements showed that the samples have satisfactory magnetizations at 10K and room temperature. The sample with x=0.15 exhibited the highest magnetic saturation at room temperature and it was applied in an ACB technique which showed satisfactory results
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Martins, Murillo Longo. "Síntese e caracterização de ferritas de manganês e zinco visando aplicação como agente de contraste em diagnóstico médico (biosusceptometria de corrente alternada) /." Bauru : [s.n.], 2011. http://hdl.handle.net/11449/99701.

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Resumo: Para o aprimoramento de técnicas de diagnóstico e tratamentos de doenças o desenvolvimento de materiais magnéticos é de primordial importância. Neste trabalho as ferritas de manganês e zindo de fórmula geral Mn(1-x)ZNxFe204, onde x assume os valores entre 0,15 e 0,30, foram preparadas pelo método dos precursores poliméricos e caracterizadas por: análises térmicas (termogravimetria associada com análise térmica diferencial (TG/DTA), análise composicional semi-quantitativa por energia dispersiva de raios X (EDX), difratometria de raios X (DRX), refinamento estrutural (Método de Rietveld), adsorção de N2 a 77K (BET), microscopia eletrônica de varredura (MEV), microscopia óptica, espectroscopia de absorção atômica (testes de lixiviação) e medidas de susceptibilidade e permeabilidade magnética. As amostras de ferritas foram também revestidas com quitosana e analisadas com algumas dessas técnicas. Os materiais foram desenvolvidos com o objetivo de utilizá-los como rastreador em biosusceptometria de corrente alternada(BAC), um método de diagnóstico. O método de síntese empregado proporcionou materiais monofásicos em ferrita com baixa porosidade e área superficial. Os materiais apresentaram baixa lixiviação de metais em soluções que simulam os meios fisiológicos do trato gastrointestinal. O revestimento com quitosana foi eficiente suprimindo a dissolução de metais em meios com pHs 7,5 e 6,8. Em pH 1,2, o revestimento se mostrou menos eficiente, porém, ainda assim foi capaz de reduzir a dissolução das espécies que constituem a ferrita. Quanto ao comportamento magnético, as amostras apresentaram magnetizações satisfatórias em 10K e em temperatura ambiente. A amostra contendo zinco a x=0,15 apresentou a mais alta saturação magnética em temperatura ambiente e foi utilizada em um teste com a técnica de BAC apresentando resultados satisfatórios
Abstract: The development of magnetic materials is of primary importance for the improvement of diagnostic techniques and treatments of diseases. In this work, the manganese and zinc ferrites with general formula of Mn(1-x)ZNxFe204 and 0,15< x <0,30, was prepared by polymeric precursor method and characterized by the physical techniques as: thermal analysis [thermogravimetry and differential thermal analysis (TG/DTA)], ssemi-quantitative analysis of the composition by energy dispersive X ray (EDX), X ray diffractometry (XRD), structural refinement (Rietveld Method), N2 adsorption analysis at 77k (BET), scanning electron microscopy (SEM), optical microscopy, atomic absorption spectroscopy (lixiviation test) and magnetic susceptibility measurements. Chitosan coated samples were also prepared which were analyzed by some of those technique. The materials were developed to be used as a tracer in the alternating current biosusceptometry (ACB), a diagnostic method. The employed synthesis method provided monophasic samples of ferrites with low porosity and surface area. The materials showed low metal solubility in the media that simulate gastrointestinal tract solutions. The chitosan coating was efficient to suppress the metal dissolution in solutions with pHs 7.5 and 6.8. In pH=1.2 medium, the coating was not efficient, but still reduced the resolution of ferrite components. The magnetic measurements showed that the samples have satisfactory magnetizations at 10K and room temperature. The sample with x=0.15 exhibited the highest magnetic saturation at room temperature and it was applied in an ACB technique which showed satisfactory results
Orientador: Margarida Juri Saeki
Coorientador: Paulo Noronha Lisboa Filho
Banca: Luis Gallego Martinez
Banca: Andris Figueiroa Bakuzis
O programa de Pós-graduação em Ciência e Tecnologia de Materiais PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP
Mestre
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Suzuki, Paulo Atsushi. "Síntese e caracterização de compostos supercondutores Ln2-xMxCuO4-y (Ln = Pr, Nd, Sm, Eu; M= Ce, Th; 0 x 0,20) preparados pa partir de percursores sol-gel." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-28022014-143146/.

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Os compostos \'LN IND.2\'\'CU\'\'O IND. 4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\') apresentam supercondutividade quando o lantanídeo (\'LN\') é parcialmente substituído por \'CE\' ou \'TH\' e em seguida são submetidos a um tratamento térmico de redução para a remoção de uma pequena quantidade de oxigênio da estrutura. Desta forma, compostos policristalinos \'LN IND. 2-x\'\'M IND.X\'\'CU\'\'O IND.4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\'; \'M\' = \'CE\', \'TH\'; 0 \'< OU =\' X \'< OU =\' 0,20) foram preparados a partir de precursores sol-gel. A vantagem desta técnica de preparação é que os tratamentos térmicos são feitos em temperaturas abaixo da tempertura eutética, evitando a presença de uma fase líquida durante a sinterização dos materiais em estudo. A investigação da cinética de formação destes compostos foi feita através de medidas de difração de raios X e análise térmica diferencial e mostrou que os materiais preparados por processo sol-gel apresentam uma distribuição homogênea dos cátions. As propriedades supercondutoras foram investigadas através de medidas de magnetização e resistência elétrica em diversas amostras e uma ênfase foi dada às séries de \'EU IND. 2-X\'\'CE IND. X\'\'CU\'\'O IND. 4-Y\' (0 \'< OU =\' X \'< OU =\' 0,18) e o desaparecimento da supercondutividade em \'(\'SM IND. 1-X\'\'EU IND. X\') IND. 1,85\'\'CE IND. 0,15\'\'CU\'\'O IND. 4-Y\' (0 \'< OU =\' X \'< OU =\' 1). Os resultados foram interpretados a partir da adoção de um modelo de supercondutividade granular. As propriedades estruturais foram analisadas em mais de 50 amostras desta família de óxidos através de medidas de difração de raios X. O refinamento de estrutura pelo método de Rietveld permitiu concluir que a introdução de portadores em \'LN IND. 2-x\'\'M IND.X\'\'CU\'\'O IND.4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\'; \'M\' = \'CE\', \'TH\'; 0 \'< OU =\' X \'< OU =\' 0,20) ocorre através da substituição parcial do lantanídeo por \'CE\' ou \'TH\' e influencia diretamente as distâncias das ligações entre \'CU\' e \'O\'nos planos de \'CU\'\'O IND. 2\', responsáveis diretos pelas propriedades supercondutoras nesta família de óxidos supercondutores.
Polycrystalline samples of \'LN IND.2\'\'CU\'\'O IND. 4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\') exhibit superconductivity when subject to two different steps: i) substitution of \'CE\' or \'TH\' for the Ln element in the Ln2Cu04-y T\' phase parent compound; and ii) reduction of the resultant material. Polycrystalline samples of \'LN IND. 2-x\'\'M IND.X\'\'CU\'\'O IND.4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\'; \'M\' = \'CE\', \'TH\'; 0 \'< OR =\' X \'< OR =\' 0,20) were prepared through a sol-gel precursor. This chemical route was employed for producing homogeneous, pure, and microstructurally controlled ceramics at sufficiently low sintering temperatures, below the eutectic temperature. The kinetics of the phase formation was studied by x ray powder diffraction and thermal analysis. These results showed that all samples are homogeneous under the cationic point of view. Measurements of electrical resistance and magnetic susceptibility were performed mostly on polycrystalline samples belonging to the frontier where superconducting properties are suppressed in this family as \'EU IND. 2-X\'\'CE IND.X\'\'CU\'\'O IND. 4-Y\' (0 \'< OR =\' X \'< OR =\' 0,18) and \'(\'SM IND. 1-X\'\'EU IND. X\') IND. 1,85\'\'CE IND. 0,15\'\'CU\'\'O IND. 4-Y\' (0 \'< OR =\' X \'< OR =\' 1). The results were discussed within a superconducting granular scenario. Over 50 compounds of this family of oxides were characterized by x ray powder diffraction and all diffractograms were refined through Rietveld analysis. The results revealed that carriers are injected into \'CU\'\'O IND. 2\' planes through a partial substitution of \'CE\' or \'TH\' for the \'LN\' in \'LN IND. 2-x\'\'M IND.X\'\'CU\'\'O IND.4-Y\' (\'LN\'= \'PR\', \'ND\', \'SM\', \'EU\'; \'M\' = \'CE\', \'TH\'; 0 \'< OR =\' X \'< OR =\' 0,20). The dopings are accompanied by an expansion of the \'CU\'-\'O\' bond length within the \'CU\'\'O IND. 2\' planes, an essential feature for the appearance of superconductivity in these series.
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Silva, Maria Teresa da. "Análise estrutural de zeólitos pelo método de Rietveld." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-28022014-213824/.

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A primeira parte desta dissertação consiste em uma exposição de alguns aspectos do fenômeno de difração de raios X por cristais, de vários tipos estruturais de zeólitas e de uma introdução ao Método de Rietveld (MR)para refinamento de estrutura utilizando amostras policristalinas. Apresenta-se a seguir o resultado da aplicação do MR a uma amostra conhecida: a alumina Al2O3-α (Corindo). No teste foram refinados o fator de escala, o ponto zero (2θ0), os parâmetros de rede, os parâmetros atômicos posicionais e vibracionais e os parâmetros de perfil usando-se a função pseudo-Voigt. Passa-se então à aplicação do MR ao refinamento da estrutura de uma zeólita Y sinética e de três amostras da mesma zeólita após terem sido tratadas sob ação de vapor d´água e calor com (NH4) 2SO4 e com H2SO4
The first parto f this dissertation is presented some aspects of X-ray diffraction by crystals, different kind of zeolites and an introduction to the Rietveld Method (RM) of structure refinement by polycrystalline samples. The refinement of α- Al2O3 (Corindon) is then presented as a test for the use of RM. In this test the scale factor, the zero point (2θ0), the lattice parameters, the positional, vibrational atomic parameters and the profile parameters were refined using the pseudo-Voigt profile function. Next the RM is used for the structure refinement of a synthetic Y-zeolite and of three samples of the same zeolite after treatment with water vapour, heat, (NH4)2SO4 and H2SO4
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Bowden, Mark Edward. "Structural investigation of layered compounds based on the perovskite SrTiO₃." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/251802.

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PUTVINSKIS, RODRIGO. "Estudo do composto supercondutor Hg, Re-1223 por difratometria de raios X, com a aplicacao do metodo de Rietveld." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11742.

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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Antonio, Selma Gutierrez [UNESP]. "Aplicação do Método de Rietveld em caracterização estrutural e nanoestrutural do espinélio 'Ni IND. 1'- 'delta' Co'delta''Fe IND.2''O IND.4' preparado por reação de combustão." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/88466.

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Os espinélios têm como sua fórmula unitária geral (A1-iBi)[AiB2-i]O4 (0 =i =1), em que os parênteses são os sítios tetraédricos, os colchetes representam os sítios octaédricos e i é o grau de inversão que representa a distribuição dos cátions na rede cristalográfica. Para i igual a 1 o espinélio é chamado de inverso e tem os cátions distribuídos nos sítios tetraédrico e octaédrico de acordo com a fórmula (B)[AB]O4 e igual a 0 o espinélio é chamado de normal com a fórmula (A)[B2]O4, e para 0 < i < 1 os cátions A e B estão distribuídos entre os dois sítios randomicamente e são chamados de parcialmente invertidos ou mistos. As propriedades desses materiais dependem dos tipos de cátions e do grau de inversão. Neste trabalho utilizamos o processo de combustão, o qual tem sido apresentado como um método eficiente para a produção de partículas nanométricas, para a obtenção do sistema Ni1-d Co d Fe2O4 (d = 0; o; u; ; 1). Os materiais resultantes foram caracterizados usando o método de Rietveld para determinar a distribuição dos cátions nos sítios tetraédrico e octaédrico. Análises de espectroscopia Mössbauer foram utilizadas para corroborar os resultados obtidos pelo Método de Rietveld. A principal variável para promover a síntese de óxidos por reação de combustão e otimizá-la é a razão combustível/oxidante, que foram variadas de 1X (estequiométrica), 1,5X e 2X (dobro) e estabelecida o dobro para o desenvolvimento do trabalho. Observamos também, indicações que a razão combustível/oxidante deve variar para cada estequiometria (d ), e que o Co e Ni ocupam apenas os sítios octaédricos. O método de Rietveld e a luz síncrotron permitiram a determinação da estequiometria em cada composição, e os cálculos de microdeformação mostram a existência de flutuação composicional.
The spinels have the general unity formulae (A1-iBi)[AiB2-i]O4 (0 =i =1), where () represents the tetrahedral sites, [ ] represents the octahedral sites and i is the degree of inversion that represents the distribution of cations in the crystal lattice. For i equal to 1 it is the inverted spinel (B)[AB]O4 and i = 0 it is the normal spinel (A)[B2]O4, and for 0 < i < 1 the cations A and B are randomly distributed between the two sites. The properties of these materials depend on the types of cations and the degree of inversion. In this work we use the combustion process, which has been presented as an efficient method for the production of nanometrics particles, for the attainment of the system Ni1-d Co d Fe2O4 (d = 0; o; u; ; 1). The resulting materials were characterized using the Rietveld Method (RM) to determine the cations distribution in the tetrahedral and octahedral sites. Analyses of Mössbauer spectroscopy carried through by E. Miola and H. Rechenberg had been also used to corroborate the results obtained using Rietveld Method. The main variable to promote the oxide synthesis through combustion reaction is the fuel/oxidant ratio that, in this work, varied from stoichiometric (ratio = 1) up to two times (ratio = 2). We observe that the ratio varies from one stoichiometry to another(d ), and that Co and Ni occupy only the octahedral sites. We observe, also, that the procedure is not yet adjusted to get itself homogeneous material, since the materials present particles with very varied sizes and degree of agglomeration. The Rietveld method and the synchrotron light allowed the determination of the stoichiometry for each composition.
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Carvalho, Jesiel Freitas. "Crescimento e caracterização de monocristais fotorreativos: BSO e BTO." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-14012009-093345/.

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Neste trabalho crescemos monocristais de Bi12SiO20 (BSO) e de Bi12TiO20 (BTO). Os cristais de BSO foram crescidos pela técnica de Czochralski a partir da fase líquida com composição molar 6Bi2O3:1SiO2. Os melhores resultados foram obtidos para taxas de puxamento entre 1 e 2,5mm/h, a velocidade de rotação foi mantida constante em 20rpm. Os cristais de BTO foram crescidos pelo método top-seeded solution Growth (TSSG) a partir da composição molar 10Bi2O3:1SiO2, com taxas de puxamento menores que 0,3mm/h e velocidade de rotação entre 16 e 30 rpm. A qualidade dos cristais foi avaliada utilizando microscopia óptica e eletrônica, corrosão seletiva e raios-x. Por microscopia óptica identificamos os defeitos macroscópicos e discutimos sua natureza e possíveis causas. Utilizando a técnica de ataque químico seletivo, analisamos a morfologia das figuras de ataque e estimamos a densidade de deslocações. Visando identificar defeitos de estequiometria, fizemos medidas de composição por microanálise eletrônica. Para a caracterização cristalográfica, calculamos o parâmetro de rede por difração de raios-x usando o método do pó e confirmamos a estrutura cristalográfica através do método de Rietveld. E, ainda, medimos a atividade óptica que é uma constante característica dos cristais.
In this work we grew Bi12SiO20 (BSO) and Bi12TiO20 single crystals. The BSO crystals have been grown from the melt composition of 6Bi2O3:1SiO2 by the Czochralski method. The best results were obtained at pulling rates from 1 to 2.5m/h, the rotation rate of 20rpm was constant. The BTO crystals have been grown by the top-seeded solution growth technique from a 10Bi2O3:1SiO2 solution with pulling rates less than 0.3mm/h and rotation rates from 16 to 30rpm. The crystal quality was examined by optical and scanning electron microscopy, selective etching, and x-ray diffraction. We identified the macroscopic defects by optical microscopy and discussed their nature and probable origin. Using selective etching, we analyzed the etching pits morphology and evaluated the dislocation density. To identify stoichiometric defects, composition measurements by electron probe microanalysis were made. To obtain crystallographic characterization, we calculated the cell parameter by powder method x-ray diffraction and used the Rietveld method to verify the crystallographic structure. And, also, we measured the optical activity, a constant of the crystals.
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Antoniassi, Juliana Lívi. "A difração de raios X com o método de Rietveld aplicada a bauxitas de Porto Trombetas, PA." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3134/tde-23112010-090249/.

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O projeto enfocou a aplicação da difração de raios X (DRX) associada ao método de Rietveld na determinação quantitativa da composição mineralógica de bauxitas de Porto Trombetas, PA. Os resultados obtidos foram comparados com aqueles de outras ferramentas de determinação mineralógica, especificamente métodos tradicionais de caracterização de minérios e espectroscopia Mössbauer, além da correlação direta com dados de análises químicas que, atualmente, são utilizados no controle de pesquisa e processamento de bauxita. Preliminarmente, definiram-se tipos mineralógicos de minério com o recurso de análise por agrupamento de dados de difração de raios X para um conjunto de 60 amostras, englobando materiais da pesquisa mineral e do beneficiamento de bauxita pela Mineração Rio do Norte (MRN). Esse recurso permitiu otimizar o conjunto de amostras para o estudo e facilitar a definição de seqüências específicas de refinamento pelo método de Rietveld para grupos de amostras com composição mineralógica similar. A DRX-Rietveld mostrou-se relevante e eficiente no estudo de bauxitas, sendo obtidos satisfatórios valores de indicadores estatísticos de refinamento (GOF e Rwp), além de elevada correlação linear com as demais metodologias aplicadas, particularmente no que se refere aos maiores constituintes das amostras, essencialmente gibbsita e argilominerais. No caso de óxi-hidróxidos de ferro (basicamente hematita, goethita e uma fase de Fe3+ de baixa cristalinidade), com proporções inferiores a 20% nas amostras, verificou-se que parte desses minerais praticamente não foi detectada por DRXRietveld visto o grau de cristalinidade dessas fases, conforme observado por microscopia eletrônica de varredura e espectroscopia Mössbauer.
This research concerns the application of X-ray diffraction (XRD) with Rietveld method in order to determinate the mineralogical composition of bauxites from Porto Trombetas, PA. The results were compared with the mineralogical composition obtained by mineral separations supported by chemical analysis and Mössbauer spectroscopy, as well as correlated with XRF chemical analysis and selective dissolution chemical analysis, that routinely support bauxite mineral research, mining operation as well as mineral processing. Previously, a definition of mineralogical types was provided by cluster analysis of a 60 samples set of diffractograms, corresponding to geological research and beneficiation products from Mineração Rio do Norte (MRN). This tool simplified the analysis of a large number of data for the study and helped to establish the Rietveld refinement strategies for clusters of samples with similar mineralogical compositions. XRD with Rietveld method showed to be relevant and efficient for bauxite study, giving satisfactory statistical evaluation parameters (GOF and Rwp), besides high linear correlation with the others mineralogical methods for the major minerals, essentially gibbsite and clay minerals. For oxi-hydroxides minerals (basically hematite, goethite and a low crystallinity Fe3+ phase), with proportions bellow 20 percent of the samples, it could be seen that part of these minerals was not detected by XRD and so not evaluated by Rietveld quantification method, since they present low crystallinity as observed by scanning electron microscopy and Mössbauer spectroscopy.
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Sanches, Edgar Aparecido. "Caracterização pelo método de Rietveld do óxido de alumínio recuperado de sensores dosimétricos e estudo de parâmetros envolvidos no processo de recuperação." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-17112014-100544/.

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Corundum ou safira (α − Al2O3) é um importante material tecnológico, utilizado em inúmeras aplicações ópticas e eletrônicas e, mais recentemente, como um sensor de radiação para baixas doses e aplicações de curta exposição. Os dosímetros em estudo são provenientes da Landauer Crystal Growth Facility (Stillwater, EUA). Trata-se de fitas multicamadas, onde o material cerâmico Encontra−se aprisionado entre duas camadas de um material polimérico. O processo de recuperação do óxido de alumínio contido nestes sensores, pré − definido, é realizado na empresa SAPRA S⁄A. Este trabalho envolve a caracterização dos materiais que compõem o dosímetro e, principalmente, a caracterização do produto final obtido, verificando se ocorreram mudanças em suas propriedades dosimétricas após passar por todo o processo. Desta maneira, este estudo está voltado para a recuperação do Al2O3 a nível de processo industrial, visando a obtenção de um produto que conserve suas características estruturais e que mantenha suas propriedades dosimétricas
Corundum or sapphire (α − Al2O3) is an important technological material in many optical and electronic applications and, more recently, as a radiation detector. Dosimeters are provided by Landauer Crystal Growth Facility (Stillwater, USA) which consist of a multilayer tape made out mainly of an aluminum oxide layer enfolded by two layers of a polymeric material. The recovering process of the aluminum oxide is undertaken by Sapra S⁄A. This work comprises the characterization of the constituent material of the dosimeter, especially the final product, concerning to the possible change that could occur in the dosimetry properties after the recuperation process of the aluminum oxide. Therefore, this work is looking forward a industrial recovering process which assures a good quality of the final product
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Books on the topic "Rietveld method"

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Strienitz, Rolf. Bildung und quantitative Bestimmung von tobermoritischen Phasen in dampfgehärteten Baustoffen mittels Röntgenverfahren nach RIETVELD. Freiberg: Technische Universität Bergakademie Freiberg, 2006.

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Young, R. A. Rietveld Method. Oxford University Press, 1995.

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1921-, Young R. A., ed. The Rietveld method. [Chester, England]: International Union of Crystallograhy, 1993.

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Will, Georg. Powder Diffraction: The Rietveld Method and the Two-Stage Method. Springer-Verlag Berlin and Heidelberg GmbH & Co. K, 2005.

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Young, R. A. The Rietveld Method (International Union of Crystallography Monographs on Crystallography 5). Oxford University Press, USA, 1995.

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Powder Diffraction: The Rietveld Method and the Two Stage Method to Determine and Refine Crystal Structures from Powder Diffraction Data. Springer, 2005.

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Will, Georg. Powder Diffraction: The Rietveld Method and the Two Stage Method to Determine and Refine Crystal Structures from Powder Diffraction Data. Springer Berlin / Heidelberg, 2010.

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Book chapters on the topic "Rietveld method"

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Albinati, A., and B. T. M. Willis. "The Rietveld method." In International Tables for Crystallography, 710–12. Chester, England: International Union of Crystallography, 2006. http://dx.doi.org/10.1107/97809553602060000614.

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Madsen, Ian C., Nicola V. Y. Scarlett, Daniel P. Riley, and Mark D. Raven. "Quantitative Phase Analysis Using the Rietveld Method." In Modern Diffraction Methods, 283–320. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527649884.ch10.

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Ran, Xu, Jun Guo Ran, Li Gou, Ji Yong Chen, and Jiao Min Luo. "Structure of Carbonated Hydroxyapatite Based on Rietveld Method." In High-Performance Ceramics V, 1187–89. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/0-87849-473-1.1187.

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Sakthivel, A., A. D. French, B. Eckhardt, and R. A. Young. "Application of the Rietveld Crystal Structure Refinement Method to Cellotetraose." In ACS Symposium Series, 68–87. Washington, DC: American Chemical Society, 1987. http://dx.doi.org/10.1021/bk-1987-0340.ch004.

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Takata, Masaki, Eiji Nishibori, and Makoto Sakata. "Structures of Fullerides and Endohedral Metallofullerenes Found by MEM/Rietveld Method." In Endofullerenes, 185–216. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-015-9938-2_9.

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Takata, Masaki, Eiji Nishibori, Makoto Sakata, and H. Shinohara. "Charge Density Level Structures of Endohedral Metallofullerenes by the MEM/Rietveld Method." In Fullerene-Based Materials, 59–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b94379.

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Boulassel, Fatma Zohra, Benabbas Abderrahim, and Rekaik Mouna. "Application of the Rietveld Method in the Study of Phases in High Chromium Cast Irons." In Proceedings of the Third International Symposium on Materials and Sustainable Development, 306–12. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-89707-3_35.

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Li, Guangshi, Hongwei Cheng, Cong Xu, Changyuan Lu, Xionggang Lu, Xingli Zou, and Qian Xu. "Mineralogical Analysis of Nickel/Copper Polymetallic Sulfide Ore by X-Ray Diffraction Using Rietveld Method." In Characterization of Minerals, Metals, and Materials 2016, 67–74. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-48210-1_8.

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Li, Guangshi, Hongwei Cheng, Cong Xu, Changyuan Lu, Xionggang Lu, Xingli Zou, and Qian Xu. "Mineralogical Analysis of Nickel/Copper Polymetallic Sulfide ORE by X-Ray Diffraction Using Rietveld Method." In Characterization of Minerals, Metals, and Materials 2016, 65–74. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119263722.ch8.

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Salvador, V. L. R., and Nelson Batista de Lima. "Separation of Effects due to Superimposition Using the Rietveld Method in Spectra Obtained by WDXRF." In Materials Science Forum, 59–64. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-423-5.59.

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Conference papers on the topic "Rietveld method"

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LISOVYTSKIY, D., J. PIELASZEK, and V. N. BAUMER. "RIETVELD METHOD IN THE ANALYSIS OF NANOCRYSTALLINE LITHIUM-MANGANESE SPINEL." In Proceedings of the XIX Conference. WORLD SCIENTIFIC, 2004. http://dx.doi.org/10.1142/9789812702913_0014.

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Balaji, V., S. Senthilkumaran, and P. Thangadurai. "Quantitative phase analysis of Mg:ZrO2 nanoparticles by Rietveld refinement method." In SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872577.

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Bolmgren, H., T. Lundström, and S. Okada. "Structure refinement of the boron suboxide B6O by the Rietveld method." In Boron-rich solids. AIP, 1991. http://dx.doi.org/10.1063/1.40868.

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Seema and Sunil Rohilla. "Rietveld refinement and structural characterization of powder ZnFe2O4 synthesized through coprecipitation method." In ADVANCES IN BASIC SCIENCE (ICABS 2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5122522.

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Liu, Honghua, Piqi Zhao, Shoude Wang, Chenchen Gong, and Lingchao Lu. "Rietveld Quantitative Analysis of Amorphous Phase in Slag by Internal Standard Method." In 2018 10th International Conference on Measuring Technology and Mechatronics Automation (ICMTMA). IEEE, 2018. http://dx.doi.org/10.1109/icmtma.2018.00098.

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Preeti and Sunil Rohilla. "Rietveld refinement and structural characterization of (La1.2Sr0.8) InMnO6 nanopowders synthesized by coprecipitation method." In ADVANCES IN BASIC SCIENCE (ICABS 2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5122589.

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de Almeida, W. L., A. Brylak, N. F. B. Giarola, S. C. Saab, L. F. Pires, and A. M. Brinatti. "Refinement of Goethite and Quartz from a Brazilian soil through the Rietveld Method." In International Symposium on Crystallography. São Paulo: Editora Edgard Blücher, 2015. http://dx.doi.org/10.5151/phypro-sic100-063.

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Freitas, B. A., C. S. Silveira, J. A. Resende, and R. B. V. Azeredo. "Preparing a rock sample to Rietveld analysis: What is the best grinding method?" In International Symposium on Crystallography. São Paulo: Editora Edgard Blücher, 2015. http://dx.doi.org/10.5151/phypro-sic100-068.

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Hussain, Farouq Ibrahim, and Amel Jasim Abbas. "Structural analysis for Nil-xZnx Fe2O4 spinel ferrite by PXRD and rietveld refinement method." In TECHNOLOGIES AND MATERIALS FOR RENEWABLE ENERGY, ENVIRONMENT AND SUSTAINABILITY: TMREES21Gr. AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0093070.

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Kumar, Sudhish, S. N. Dolia, R. K. Singhal, P. Predeep, Mrinal Thakur, and M. K. Ravi Varma. "Application of Rietveld Method to the Structural Characteristics of some Bulk and Nanocrystalline Materials." In OPTICS: PHENOMENA, MATERIALS, DEVICES, AND CHARACTERIZATION: OPTICS 2011: International Conference on Light. AIP, 2011. http://dx.doi.org/10.1063/1.3646781.

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