{"title":"Rietveld Refinement and Vibrational Spectroscopic Study of U-Bearing Natural Celestine","authors":"Fathi Allouche, Houda Ettoumi, Amina Ammous, Mohamed Toumi","doi":"10.1007/s13538-024-01564-1","DOIUrl":null,"url":null,"abstract":"<p>This study presents a comprehensive inquiry into the structural refinement and Raman spectroscopy of natural barium strontium sulfate, characterized as Sr<sub>0.967(2)</sub>Ba<sub>0.030(2)</sub>U<sub>0.0022(6)</sub>Y<sub>0.0012(6)</sub>SO<sub>4</sub>. The crystal structure of orthorhombic sulfate celestine is meticulously refined using Rietveld methods with conventional powder X-ray diffraction data, optimizing the structural model within space group <i>Pnma</i> (<i>Z</i> = 4). The ultimate reliability factors, namely <i>χ</i><sup>2</sup> = 5.6, <i>R</i><sub>F</sub> = 3.6, and <i>R</i><sub>Bragg</sub> = 4.65, confirm the outstanding quality of the refinement process. These factors serve as indicators of the degree to which the refined crystal structure in alignment with the experimental data. In this case, the values suggest a high level of accuracy and precision in the refinement, reinforcing the reliability of the obtained structural model for the celestine crystal. The resulting unit cell parameters are reported as <i>a</i> = 8.372(9) Å, <i>b</i> = 5.357(6) Å, <i>c</i> = 6.877(7) Å, and <i>V</i> = 308.42(7) Å<sup>3</sup>. The average <M-O> Vinograd et al. (Appl. Geochem. 89, 59–74, 2018) distance is 2.832(6) Å, while the corresponding average <S-O> Baker and Bloomer (Geochim. Cosmochim. 52, 335–339, 1988) distance is 1.497(4) Å. This investigation confirms the isostructural nature of the celestine solid solution with pure SrSO<sub>4</sub> and barite (BaSO<sub>4</sub>). Chemical analysis through X-ray fluorescence provides the empirical formula for celestine as (Sr<sub>0.979</sub>Ba<sub>0.013</sub>U<sub>0.001</sub>Y<sub>0.005</sub>)SO<sub>4</sub>. Additionally, the application of Vegard’s law for unit cell parameters consistently aligns with the chemical formulas obtained from Rietveld refinement and X-ray fluorescence analysis, underscoring the reliability of Vegard’s law in predicting compound composition. Distinctive vibrational modes in natural celestine are unveiled through Raman spectroscopy, revealing a composition diverging from typical celestine. The observed shift in Raman bands is ascribed to the incorporation of Ba, U, and Y into the celestine lattice, resulting in a solid solution denoted as Sr<sub>1-x</sub> (Ba, U, Y)ₓSO<sub>4</sub>. The chemical formula derived through the application of Vegard’s law for <i>ν</i><sub>1</sub>(SO<sub>4</sub>) is reported as Sr<sub>0.977</sub> Ba<sub>0.023</sub>SO<sub>4</sub>. This formula closely corresponds to the formulation presented earlier.</p>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.5000,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Brazilian Journal of Physics","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1007/s13538-024-01564-1","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
This study presents a comprehensive inquiry into the structural refinement and Raman spectroscopy of natural barium strontium sulfate, characterized as Sr0.967(2)Ba0.030(2)U0.0022(6)Y0.0012(6)SO4. The crystal structure of orthorhombic sulfate celestine is meticulously refined using Rietveld methods with conventional powder X-ray diffraction data, optimizing the structural model within space group Pnma (Z = 4). The ultimate reliability factors, namely χ2 = 5.6, RF = 3.6, and RBragg = 4.65, confirm the outstanding quality of the refinement process. These factors serve as indicators of the degree to which the refined crystal structure in alignment with the experimental data. In this case, the values suggest a high level of accuracy and precision in the refinement, reinforcing the reliability of the obtained structural model for the celestine crystal. The resulting unit cell parameters are reported as a = 8.372(9) Å, b = 5.357(6) Å, c = 6.877(7) Å, and V = 308.42(7) Å3. The average <M-O> Vinograd et al. (Appl. Geochem. 89, 59–74, 2018) distance is 2.832(6) Å, while the corresponding average <S-O> Baker and Bloomer (Geochim. Cosmochim. 52, 335–339, 1988) distance is 1.497(4) Å. This investigation confirms the isostructural nature of the celestine solid solution with pure SrSO4 and barite (BaSO4). Chemical analysis through X-ray fluorescence provides the empirical formula for celestine as (Sr0.979Ba0.013U0.001Y0.005)SO4. Additionally, the application of Vegard’s law for unit cell parameters consistently aligns with the chemical formulas obtained from Rietveld refinement and X-ray fluorescence analysis, underscoring the reliability of Vegard’s law in predicting compound composition. Distinctive vibrational modes in natural celestine are unveiled through Raman spectroscopy, revealing a composition diverging from typical celestine. The observed shift in Raman bands is ascribed to the incorporation of Ba, U, and Y into the celestine lattice, resulting in a solid solution denoted as Sr1-x (Ba, U, Y)ₓSO4. The chemical formula derived through the application of Vegard’s law for ν1(SO4) is reported as Sr0.977 Ba0.023SO4. This formula closely corresponds to the formulation presented earlier.
期刊介绍:
The Brazilian Journal of Physics is a peer-reviewed international journal published by the Brazilian Physical Society (SBF). The journal publishes new and original research results from all areas of physics, obtained in Brazil and from anywhere else in the world. Contents include theoretical, practical and experimental papers as well as high-quality review papers. Submissions should follow the generally accepted structure for journal articles with basic elements: title, abstract, introduction, results, conclusions, and references.