X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors
A method to analyze powder-diffraction line broadening is proposed and applied to some novel high-Tc superconductors. Assuming that both size-broadened and strain-broadened profiles of the pure-specimen profile are described with a Voigt function, it is shown that the analysis of Fourier coefficient...
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| Format: | Online |
| Language: | English |
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[Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology
1993
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| Online Access: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4914239/ |
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pubmed-49142392017-01-04 X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors Balzar, Davor Article A method to analyze powder-diffraction line broadening is proposed and applied to some novel high-Tc superconductors. Assuming that both size-broadened and strain-broadened profiles of the pure-specimen profile are described with a Voigt function, it is shown that the analysis of Fourier coefficients leads to the Warren-Averbach method of separation of size and strain contributions. The analysis of size coefficients shows that the “hook” effect occurs when the Cauchy content of the size-broadened profile is underestimated. The ratio of volume-weighted and surface-weighted domain sizes can change from ~1.31 for the minimum allowed Cauchy content to 2 when the size-broadened profile is given solely by a Cauchy function. If the distortion co-efficient is approximated by a harmonic term, mean-square strains decrease linearly with the increase of the averaging distance. The local strain is finite only in the case of pure-Gauss strain broadening because strains are then independent of averaging distance. Errors of root-mean-square strains as well as domain sizes were evaluated. The method was applied to two cubic structures with average volume-weighted domain sizes up to 3600 Å, as well as to tetragonal and orthorhombic (La-Sr)2CuO4, which exhibit weak line broadenings and highly overlapping reflections. Comparison with the integral-breadth methods is given. Reliability of the method is discussed in the case of a cluster of the overlapping peaks. The analysis of La2CuO4 and La1.85M0.15CuO4(M = Ca, Ba, Sr) high-Tc superconductors showed that microstrains and incoherently diffracting domain sizes are highly anisotropic. In the superconductors, stacking-fault probability increases with increasing Tc; microstrain decreases. In La2CuO4, different broadening of (h00) and (0k0) reflections is not caused by stacking faults; it might arise from lower crystallographic symmetiy. The analysis of Bi-Cu-O superconductors showed much higher strains in the [001] direction than in the basal a-b plane. This may be caused by stacking disorder along the c-axis, because of the two-dimensional weakly bonded BiO double layers. Results for the specimen containing two related high-Tc phases indicate a possible mechanism for the phase transformation by the growth of faulted regions of the major phase. [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology 1993 /pmc/articles/PMC4914239/ /pubmed/28053477 http://dx.doi.org/10.6028/jres.098.026 Text en https://creativecommons.org/publicdomain/zero/1.0/ The Journal of Research of the National Institute of Standards and Technology is a publication of the U.S. Government. The papers are in the public domain and are not subject to copyright in the United States. Articles from J Res may contain photographs or illustrations copyrighted by other commercial organizations or individuals that may not be used without obtaining prior approval from the holder of the copyright. |
| repository_type |
Open Access Journal |
| institution_category |
Foreign Institution |
| institution |
US National Center for Biotechnology Information |
| building |
NCBI PubMed |
| collection |
Online Access |
| language |
English |
| format |
Online |
| author |
Balzar, Davor |
| spellingShingle |
Balzar, Davor X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| author_facet |
Balzar, Davor |
| author_sort |
Balzar, Davor |
| title |
X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| title_short |
X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| title_full |
X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| title_fullStr |
X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| title_full_unstemmed |
X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors |
| title_sort |
x-ray diffraction line broadening: modeling and applications to high-tc superconductors |
| description |
A method to analyze powder-diffraction line broadening is proposed and applied to some novel high-Tc superconductors. Assuming that both size-broadened and strain-broadened profiles of the pure-specimen profile are described with a Voigt function, it is shown that the analysis of Fourier coefficients leads to the Warren-Averbach method of separation of size and strain contributions. The analysis of size coefficients shows that the “hook” effect occurs when the Cauchy content of the size-broadened profile is underestimated. The ratio of volume-weighted and surface-weighted domain sizes can change from ~1.31 for the minimum allowed Cauchy content to 2 when the size-broadened profile is given solely by a Cauchy function. If the distortion co-efficient is approximated by a harmonic term, mean-square strains decrease linearly with the increase of the averaging distance. The local strain is finite only in the case of pure-Gauss strain broadening because strains are then independent of averaging distance. Errors of root-mean-square strains as well as domain sizes were evaluated. The method was applied to two cubic structures with average volume-weighted domain sizes up to 3600 Å, as well as to tetragonal and orthorhombic (La-Sr)2CuO4, which exhibit weak line broadenings and highly overlapping reflections. Comparison with the integral-breadth methods is given. Reliability of the method is discussed in the case of a cluster of the overlapping peaks. The analysis of La2CuO4 and La1.85M0.15CuO4(M = Ca, Ba, Sr) high-Tc superconductors showed that microstrains and incoherently diffracting domain sizes are highly anisotropic. In the superconductors, stacking-fault probability increases with increasing Tc; microstrain decreases. In La2CuO4, different broadening of (h00) and (0k0) reflections is not caused by stacking faults; it might arise from lower crystallographic symmetiy. The analysis of Bi-Cu-O superconductors showed much higher strains in the [001] direction than in the basal a-b plane. This may be caused by stacking disorder along the c-axis, because of the two-dimensional weakly bonded BiO double layers. Results for the specimen containing two related high-Tc phases indicate a possible mechanism for the phase transformation by the growth of faulted regions of the major phase. |
| publisher |
[Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology |
| publishDate |
1993 |
| url |
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4914239/ |
| _version_ |
1613597140284604416 |