Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

1972 ◽  
Vol 50 (22) ◽  
pp. 3648-3666 ◽  
Author(s):  
François Brisse ◽  
David J. Stewart ◽  
V. Seidl ◽  
Osvald Knop
Keyword(s):  
Crystal Structures ◽  
Crystal Chemistry ◽  
Powder Diffraction ◽  
Mixed Crystals ◽  
Powder Diffractometer ◽  
Pyrochlore Type ◽  
Diffraction Patterns ◽  
Relationship Of ◽  
The Relationship ◽  
Related Compounds

The cubic pyrochlores Cd2Nb2O7, Cd2Ta2O7, Sn2Nb2O7, Sn2Ta2O7. Cd2Sb7O7, Ca2Sb2O7, Mn2Sb2O7, Pb2Sb2O7, and related compounds were prepared and investigated by a number of methods. On heating above 700°. Ca2Sb2O7(pyrochlore) transformed to Ca2Sb2O7(weberite), while Pb2Sb2O7(pyrochlore) changed to a rhombohedrally distorted Pb2Sb2O7 pyrochlore. Refinement of the crystal structures of Cd2Nb2O7 and Cd2Ta2O7 from powder diffractometer intensities yielded 0.434(2) and 0.434(3) respectively as the best estimates of x(O2). Specimens of natural bindheimite and stibiconite were also examined. Stibiconite from San Luis Potosi (Mexico) was shown, on the evidence of its Mössbauer 121Sb spectrum, to contain Sb(V) and Sb(III) in the approximate ratio of 0.2.BaCd2Cl6•5H2O and BaCd2Cl6•2H2O both give powder diffraction patterns of the pyrochlore type. The chlorine could be partially replaced by Br to give mixed crystals BaCd2Cl6−zBrz•5H2O almost up to z = 2.The crystal chemistry of 2–5 oxide pyrochlores and the relationship of the weberite to the pyrochlore phases are discussed.

Two examples of quantitative analysis by simulated X-ray powder diffraction patterns

Clay Minerals ◽  
1982 ◽  
Vol 17 (4) ◽  
pp. 393-399
Author(s):  
C. E. Corbato ◽  
R. T. Tettenhorst
Keyword(s):  
Quantitative Analysis ◽  
Pattern Matching ◽  
Powder Diffraction ◽  
X Ray ◽  
Quantitative Estimates ◽  
Powder Diffractometer ◽  
Alternative Method ◽  
Two Samples ◽  
Natural Mixture ◽  
Diffraction Patterns

AbstractQuantitative estimates were made by visually matching computer-simulated with experimental X-ray powder diffractometer patterns for two samples. One was a natural mixture of dickite and nacrite in about equal proportions. The second sample contained mostly quartz with corundum and mullite in small (0.5–1%) amounts. Percentages deduced from pattern matching agreed to within ±10% of the weight fractions of the components determined by an alternative method of analysis.

scholarly journals High-throughput powder diffraction. II. Applications of clustering methods and multivariate data analysis

2004 ◽  
Vol 37 (2) ◽  
pp. 243-252 ◽  
Author(s):  
Gordon Barr ◽  
Wei Dong ◽  
Christopher J. Gilmore
Keyword(s):  
Powder Diffraction ◽  
High Throughput ◽  
Inorganic Compounds ◽  
Computer Software ◽  
Principal Component ◽  
Clustering Methods ◽  
Visualization Tools ◽  
Diffraction Patterns ◽  
Pure Phases ◽  
Related Compounds

In high-throughput crystallography, it is possible to accumulate over 1000 powder diffraction patterns on a series of related compounds, often polymorphs. A method is presented that can analyse such data, automatically sort the patterns into related clusters or classes, characterize each cluster and identify any unusual samples containing, for example, unknown or unexpected polymorphs. Mixtures may be analysed quantitatively if a database of pure phases is available. A key component of the method is a set of visualization tools based on dendrograms, cluster analysis, pie charts, principal-component-based score plots and metric multidimensional scaling. Applications to pharmaceutical data and inorganic compounds are presented. The procedures have been incorporated into thePolySNAPcommercial computer software.

scholarly journals The crystal chemistry of cowlesite

1992 ◽  
Vol 56 (385) ◽  
pp. 575-579 ◽  
Author(s):  
Giovanna Vezzalini ◽  
Gilberto Artioli ◽  
Simona Quartieri ◽  
Harry Foy
Keyword(s):  
Northern Ireland ◽  
Crystal Chemistry ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Chemical Data ◽  
Orthorhombic Unit Cell ◽  
X Ray ◽  
Compositional Range ◽  
Diffraction Patterns ◽  
New Occurrences

AbstractCowlesite specimens from nine new occurrences in Northern Ireland and from eight localities previously reported in the literature, were crystal-chemically characterised. The chemical data for a total of 25 samples indicate a composition close to the stoichiometric formula for cowlesite and a very limited compositional range. X-ray powder diffraction spectra were performed on 8 samples. The crystallographic unit cell permit a proper indexing of the X-ray powder diffraction patterns as orthorhombic, unit cell constants close to a 23.3, b 30.6, c 25.0 Å and doubled with respect to those originally reported in literature. The powder pattern and the TG curve arc reported for an unidentified mineral species associated with cowlesite in one of the samples from Northern Ireland.

scholarly journals PolySNAP: a computer program for analysing high-throughput powder diffraction data

2004 ◽  
Vol 37 (4) ◽  
pp. 658-664 ◽  
Author(s):  
Gordon Barr ◽  
Wei Dong ◽  
Christopher J. Gilmore
Keyword(s):  
Computer Program ◽  
Powder Diffraction ◽  
High Throughput ◽  
Three Dimensional ◽  
Principal Component ◽  
Visualization Tools ◽  
Diffraction Patterns ◽  
Pure Phases ◽  
Related Compounds ◽  
High Throughput Crystallography

In high-throughput crystallography experiments, it is possible to measure over 1000 powder diffraction patterns on a series of related compounds, often polymorphs or salts, in less than one week. The analysis of these patterns poses a difficult statistical problem. A computer program is presented that can analyse such data, automatically sort the patterns into related clusters or classes, characterize each cluster and identify any unusual samples containing, for example, unknown or unexpected polymorphs. Mixtures may be analysed quantitatively if a database of pure phases is available. A key component of the method is a set of visualization tools based on dendrograms and pie charts, as well as principal-component analysis and metric multidimensional scaling as a source of three-dimensional score plots. The procedures have been incorporated into the computer programPolySNAP, which is available commercially from Bruker-AXS.

The Crystal Structures and Powder Diffraction Patterns of the Uranium Tellurides: A Critical Review

1991 ◽  
Vol 6 (4) ◽  
pp. 204-227 ◽  
Author(s):  
Robert L. Snyder ◽  
Monte C. Nichols ◽  
Dale R. Boehme
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Critical Review ◽  
Poor Quality ◽  
Diffraction Patterns

AbstractA critical review of all the reported structures and powder diffraction patterns in the uranium telluride system has been undertaken. Our recommendations are:1. Structures that are correct:• Cubic – UTe: no experimental pattern exists. Retain calculated 15–865.• Cubic – U3Te4: retain poor quality 12-610 but adopt the pattern calculated here.• Cubic U2Te3: no experimental pattern exists. Adopt pattern calculated here.• Orthorhombic UTe2: Adopt the new pattern of Boehme et al.• Monoclinic αUTe3: Adopt the new pattern of Boehme et al.• Orthorhombic βUTe3: Adopt the pattern calculated here.• Orthorhombic UTe5: Adopt the new pattern of Boeheme et al.2. Structures in need of refinement:• Orthorhombic U2Te3: Adopt pattern calculated here over 34-807.• Hexagonal U7Te12: Adopt pattern calculated here but retain 24-1368.• Orthorhombic UTe1.78: Adopt pattern calculated here and retain our modified 21-1404 reported for U4Te7.• Orthorhombic UTe2.5: Adopt pattern calculated here.• Orthorhombic UTe3.4: Accept recent pattern of Boehme et al.3. Phases for which no structures or reliable patterns exist:• Orthorhombic U3Te4: no published pattern.• Tetragonal U3Te5: three patterns 21-1407, 34-766 and 34-896 exist but all are of very poor quality.4. Phases which probably do not exist:• Tetragonal UTe1.77• Tetragonal UTe2• Cubic UTe2• U3Te7 (21-1402)• U3Te8 (21-1406)

The ICDD/PDF Coverage of the High Tc Superconductor and Related Compounds in the A-R-Cu-O Systems (A = Ba, Sr and Ca, and R = Lanthanides and Y)

1992 ◽  
Vol 7 (3) ◽  
pp. 125-133 ◽  
Author(s):  
Winnie Wong-Ng
Keyword(s):  
Powder Diffraction ◽  
Cross Correlation ◽  
Reaction Products ◽  
Powder Diffraction File ◽  
High Tc ◽  
X Ray ◽  
High Tc Superconductor ◽  
Different Types ◽  
Diffraction Patterns ◽  
Related Compounds

AbstractA compilation has been made of the X-ray powder diffraction patterns of the high Tc superconductor and related phases in the systems of Ba-R-Cu-O, Sr-R-Cu-O and Ca-R-Cu-O, where R = yttrium and lanthanides. In addition to the patterns of compounds found in these systems, other related compounds included are cation substitution products of the high Tc phases of Ba2RCu2O6+x, potential reaction products with different types of sample containers, and selected thin-film substrates. The International Centre for Diffraction Data/Powder Diffraction file (ICDD/PDF) coverage includes Sets 1 to 41. A cross correlation of these phases with those reported in Phase Diagrams For Ceramists (PDFC), has also been completed. Results of these efforts are tabulated.

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