The Role of Monte Carlo Calculations In Quantitative Analysis

1998 ◽  
Vol 4 (S2) ◽  
pp. 232-233
Author(s):  
E. Lifshin ◽  
L. A. Peluso ◽  
R. Gauvin
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Normal Incidence ◽  
Physical Models ◽  
Generation Process ◽  
X Rays ◽  
Experimental Conditions ◽  
X Ray ◽  
High Level

In conventional quantitative electron microprobe analysis, methods like ZAF and φ(ρz), are used to convert x-ray intensity data to chemical composition utilizing equations that describe electron solid interactions, the x-ray generation process, absorption of the generated x-rays and secondary fluorescence effects. These equations capture the overall response of a sample or standard rather than consider the fate of individual electrons over time. For example, f(χ) is simply the ratio of x-rays emitted to the number generated. While for the most part these methods are built on solid physical models, the models were never exact enough to completely match measured data. Consequently, they have been modified by various adjustable parameters to ensure a high level of accuracy for a wide variety of systems and experimental conditions. However, since most of the adjustments were based on data taken at normal incidence, there has always been a question of how to obtain accurate results from tilted samples.

An Empirical Test Of A Thin-Film Analysis Routine On Bisrcacu Oxide Superconductor Precursors

1990 ◽  
Vol 48 (2) ◽  
pp. 236-237
Author(s):  
D.K. Ross ◽  
R.V. Heyman ◽  
D. Elthon
Keyword(s):  
Thin Film ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Empirical Test ◽  
X Rays ◽  
Film Analysis ◽  
X Ray ◽  
Analysis Techniques ◽  
Thin Film Analysis ◽  
Excitation Volume

Until quite recently, electron microprobe analysis techniques were limited to samples of “infinite” thickness, that is, to samples thick enough such that the entire excitation volume was contained within the material of interest. Thin film analysis was not possible with available matrix correction programs, which were based on the assumption of samples of “infinite” thickness. Now however, algorithms are available that permit analysis of thin samples.We have obtained one of the more versatile and sophisticated of these programs. In order to investigate the accuracy of this routine we have analyzed several BiSrCaCuO thin films at 15 kV and repeated the analysis at 30 kV. These films were thick enough such that at 15 kV conventional ZAF data reduction yielded acceptable totals (98-101 %) with minimal substrate x rays observed. At 30 kV, however abundant substrate x rays were observed and ZAF yielded very low totals. X-ray intensity ratios from 30 kV runs were used to estimate film thickness and matrix corrections were applied using the Waldo algorithm.

Low Z Elemental Analysis using Energy Loss Electrons in a Scanning Microscope

1973 ◽  
Vol 31 ◽  
pp. 290-291
Author(s):  
D. E. Johnson ◽  
M. Isaacson
Keyword(s):  
Production Efficiency ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Solid Angle ◽  
Collection Efficiency ◽  
Fluorescence Yield ◽  
X Rays ◽  
Scanning Microscope ◽  
Thin Sections ◽  
X Ray

Electron microprobe analysis has been used increasingly in, recent years for low Z analysis of thin biological sections. Although this technique has produced useful results, the sensitivity is limited by two main factors. First, the fluorescence yield (wK) decreases rapidly with decreasing Z. Using the value of wK (for carbon for example, only about one out of every 400 K ionizations in carbon results in a carbon x-ray. Second, this poor x-ray production efficiency is coupled with the inherently poor x-ray collection efficiency of most microprobe detectors. In thin sections the x-rays are emitted uniformly over 4TT steradians but the detector subtends only a small solid angle at the specimen. Hall estimates the collection efficiency of most diffracting detectors at 10−4 and, with the qualification of much lower peak to background ratios, he estimates the collection efficiency of solid state nondiffractive detectors as 10−4 to 10−2.

Electron microprobe analysis under conditions of non-normal Electron beam incidence

2000 ◽  
Vol 6 (S2) ◽  
pp. 922-923
Author(s):  
E. Lifshin ◽  
R. Gauvin
Keyword(s):  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Normal Incidence ◽  
Radial Symmetry ◽  
X Ray ◽  
Detection Systems ◽  
Electron Microscopes ◽  
Normal Electron ◽  
Scanning Electron Microscopes

From its inception, electron microprobe analysis was almost exclusively done under conditions of normal electron probe incidence. The radial symmetry of this geometry greatly simplified the development of quantitative equations, and these equations where further refined based on large amounts of data also collected at normal incidence. However, as x-ray detection systems where added to scanning electron microscopes (SEMs), samples were often viewed under conditions of non-normal incidence and attempts were made to modify the various correction procedures to give acceptable quantitative results. Little justification for these methods has ever been published and so the current study was undertaken to compare theoretically calculated x-ray emission from a well characterized sample, in this case NiAl (.685 wt. % Ni, .315 wt. %A1) with experimentally measured results collected as a function of tilt angle. The theoretical calculation where done using a Monte Carlo (MC) program developed by Gauvin and Lifshin.

Fundamental parameters of x-ray microanalysis: A brief introduction

1990 ◽  
Vol 48 (2) ◽  
pp. 2-3
Author(s):  
Peter Duncumb
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
X Rays ◽  
X Ray ◽  
Fundamental Parameters ◽  
The Past ◽  
Basic Physics ◽  
The Subject ◽  
Almost All ◽  
Physical Laws

It is indeed fortunate that nature has provided us with such well-defined physical laws governing the generation of x rays and their interaction with matter. This benefit has given electron microprobe analysis two major advantages over many other techniques of analysis: it can be applied to almost all elements in the periodic table and it can be applied quantitatively. Nevertheless, we are continually striving for better and better quantitation over a wider range of conditions, and there is a corresponding pressure to improve our knowledge of the physics. The purpose of this session is to identify the fundamental parameters by which these physical laws are expressed, and to explore their relative importance in determining the accuracy of which the technique is capable.The essential link between the basic physics of microprobe analysis and its useful application is the physical model used to represent the process numerically. Many such models have been proposed in the past 40 years and these are properly the subject of a separate session on quantitative analysis.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Coiraite, (Pb,Sn2+)12.5As3Fe2+Sn4+5 S28: a franckeite-type new mineral species from Jujuy Province, NW Argentina

2008 ◽  
Vol 72 (5) ◽  
pp. 1083-1101 ◽  
Author(s):  
W. H. Paar ◽  
Y. Moëlo ◽  
N. N. Mozgova ◽  
N. I. Organova ◽  
C. J. Stanley ◽  
...  
Keyword(s):  
Low Temperature ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Mineral Species ◽  
New Mineral ◽  
Hydrothermal Solutions ◽  
X Ray ◽  
New Mineral Species ◽  
Primary Mineral ◽  
The Ideal

AbstractCoiraite, ideally (Pb,Sn2+)12.5As3Fe2+Sn4+S28, occurs as an economically important tin ore in the large Ag-Sn-Zn polymetallic Pirquitas deposit, Jujuy Province, NW-Argentina. The new mineral species is the As derivative of franckeite and belongs to the cylindrite group of complex Pb sulphosalts with incommensurate composite-layered structures. It is a primary mineral, frequently found in colloform textures, and formed from hydrothermal solutions at low temperature. Associated minerals are franckeite, cylindrite, pyrite-marcasite, as well as minor amounts of hocartite, Ag-rich rhodostannite. arsenopyrite and galena. Laminae of coiraite consist of extremely thin bent platy crystals up to 50 urn long. Electron microprobe analysis (n = 31) gave an empirical formula Pb11.21As2.99Ag0.13Fe1.10Sn6.13S28.0 close to the ideal formula (Pb11.3Sn2+1.2)Σ=12.5As3Fe2+Sn4+S28. Coiraite has two monoclinic sub-cells, Q (pseudotetragonal) and H (pseudohexagonal). Q: a 5.84(1) Å, b 5.86(1) Å, c 17.32(1) Å, β 94.14(1)°, F 590.05(3) Å3, Z = 4, a:b:c = 0.997:1:2.955; H (orthogonal setting): a 6.28(1) Å, b 3.66(1) Å, c 17.33(1) Å, β 91.46(1)°, V398.01(6) Å3, Z = 2, a∶b∶c = 1.716∶1∶4.735. The strongest Debye-Scherrer camera X-ray powder-diffraction lines [d in Å, (I), (hkl)] are: 5.78, (20), (Q and H 003); 4.34, (40), (Q 004); 3.46, (30), (Q and H 005); 3.339, (20), (Q 104); 2.876, (100), (Q and H 006); 2.068, (60), (Q 220).

scholarly journals Native Gold in the Chudnoe Au-Pd-REE Deposit (Subpolar Urals, Russia): Composition, Minerals in Intergrowth and Genesis

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 451
Author(s):  
Galina Palyanova ◽  
Valery Murzin ◽  
Andrey Borovikov ◽  
Nikolay Karmanov ◽  
Sergei Kuznetsov
Keyword(s):  
Native Gold ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Gold Mineralization ◽  
Type I ◽  
Type Ii ◽  
Subpolar Urals ◽  
Type V ◽  
Impurity Elements

Composition of native gold and minerals in intergrowth with rhyolites of the Chudnoe Au-Pd-REE deposit (Subpolar Urals, Russia) was studied using optical microscopy, scanning electron microscopy, and electron microprobe analysis. Five varieties of native gold have been identified, based on the set of impurity elements and their quantities, and on intergrown minerals. Native gold in rhyolites from the Ludnaya ore zone is homogeneous and contains only Ag (fineness 720‰, type I). It is in intergrowth with fuchsite or allanite and mertieite-II. In rhyolites from the Slavnaya ore zone, native gold is heterogeneous, has a higher fineness, different sets and contents of elements: Ag, Cu, 840–860‰ (type II); Ag, Cu, Pd, 830–890‰ (III); Ag, Pd, Cu, Hg, 840–870‰ (IV). It occurs in intergrowth with fuchsite, albite, and mertieite-II (type II), or albite, quartz, and atheneite (III), or quartz, albite, K-feldspar, and mertieite-II (IV). High fineness gold (930–1000‰, type V) with low contents of Ag, Cu, and Pd or their absence occurs in the form as microveins, fringes and microinclusions in native gold II–IV. Tetra-auricupride (AuCu) is presented as isometric inclusions in gold II and platelets in the decay structures in gold III and IV. The preliminary data of a fluid inclusions study showed that gold mineralization at the Chudnoe deposit could have been formed by chloride fluids of low and medium salinity at temperatures from 105 to 230 °C and pressures from 5 to 115 MPa. The formation of native gold I is probably related to fuchsitization and allanitization of rhyolites. The formation of native gold II-V is also associated with the same processes, but it is more complicated and occurred later with a significant role of Na-, Si-, and K-metasomatism. The presence of Pd and Cu in the ores and Cr in fuchsite indicates the important role of mafic-ultramafic magmatism.

Potassic-jeanlouisite from Leucite Hill, Wyoming, USA, ideally K(NaCa)(Mg4Ti)Si8O22O2: the first species of oxo amphibole in the sodium–calcium subgroup

2019 ◽  
Vol 83 (4) ◽  
pp. 587-593
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Giancarlo Della Ventura ◽  
Gunnar Färber
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Mineralogical Association ◽  
Sodium Calcium

AbstractPotassic-jeanlouisite, ideally K(NaCa)(Mg4Ti)Si8O22O2, is the first characterised species of oxo amphibole related to the sodium–calcium group, and derives from potassic richterite via the coupled exchange CMg–1W${\rm OH}_{{\rm \ndash 2}}^{\ndash}{} ^{\rm C}{\rm Ti}_1^{{\rm 4 +}} {} ^{\rm W}\!{\rm O}_2^{2\ndash} $. The mineral and the mineral name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification, IMA2018-050. Potassic-jeanlouisite was found in a specimen of leucite which is found in the lava layers, collected in the active gravel quarry on Zirkle Mesa, Leucite Hills, Wyoming, USA. It occurs as pale yellow to colourless acicular crystals in small vugs. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(K0.84Na0.16)Σ1.00B(Ca0.93Na1.02Mg0.04${\rm Mn}_{{\rm 0}{\rm. 01}}^{2 +} $)Σ2.00C(Mg3.85${\rm Fe}_{{\rm 0}{\rm. 16}}^{2 +} $Ni0.01${\rm Fe}_{{\rm 0}{\rm. 33}}^{3 +} {\rm V}_{{\rm 0}{\rm. 01}}^{3 +} $Ti0.65)Σ5.01T(Si7.76Al0.09Ti0.15)Σ8.00O22W[O1.53F0.47]Σ2.00. The holotype crystal is biaxial (–), with α = 1.674(2), β = 1.688(2), γ = 1.698(2), 2Vmeas. = 79(1)° and 2Vcalc. = 79.8°. The unit-cell parameters are a = 9.9372(10), b = 18.010(2), c = 5.2808(5) Å, β = 104.955(2)°, V = 913.1(2) Å3, Z = 2 and space group C2/m. The strongest eight reflections in the powder X-ray pattern [d values (in Å) (I) (hkl)] are: 2.703 (100) (151); 3.380 (87) (131); 2.541 (80) ($\bar 2$02); 3.151 (70) (310); 3.284 (68) (240); 8.472 (59) (110); 2.587 (52) (061); 2.945 (50) (221,$\bar 1$51).

Crystal-chemical aspects of the roméite group, A2Sb2O6Y, of the pyrochlore supergroup

2017 ◽  
Vol 81 (6) ◽  
pp. 1287-1302
Author(s):  
Ferdinando Bosi ◽  
Andrew G. Christy ◽  
Ulf Hålenius
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structural Parameters ◽  
Chemical Information ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Structural Variations ◽  
X Ray ◽  
End Members ◽  
Charge Balancing

AbstractFour specimens of the roméite-group minerals oxyplumboroméite and fluorcalcioroméite from the Långban Mn-Fe deposit in Central Sweden were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis and infrared spectroscopy. The data obtained and those on additional roméite samples from literature show that the main structural variations within the roméite group are related to variations in the content of Pb2+, which is incorporated into the roméite structure via the substitution Pb2+→A2+ where A2+ = Ca, Mn and Sr. Additionally, the cation occupancy at the six-fold coordinated B site, which is associated with the heterovalent substitution BFe3+ + Y☐→BSb5++YO2-, can strongly affect structural parameters.Chemical formulae of the roméite minerals group are discussed. According to crystal-chemical information, the species associated with the name ‘kenoplumboroméite’, hydroxycalcioroméite and fluorcalcioroméite most closely approximate end-member compositions Pb2(SbFe3+)O6☐, Ca2(Sb5+Ti) O6(OH) and (CaNa)Sb2O6F, respectively. However, in accord with pyrochlore nomenclature rules, their names correspond to multiple end-members and are best described by the general formulae: (Pb,#)2(Sb,#)2O6☐, (Ca,#)2(Sb,#)2O6(OH) and (Ca,#)Sb2(O,#)6F, where ‘#’ indicates an unspecified charge-balancing chemical substituent, including vacancies.

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