Quantitative Electron Probe Microanalysis Research Articles

Quantitative electron microprobe analysis of aluminum, copper, and gold thin films on silicon substrates

The thicknesses of aluminum, copper, and gold thin films on silicon substrates have been measured with an electron probe microanalyzer. k ratio versus thickness calibration curves are obtained by a Monte Carlo simulation of electron scattering. The simulation results based on two energy loss models are compared. One is the continuous slowing down approximation model and another is the hybrid model for the discrete and the continuous energy loss processes. Inner shell ionizations and free electron excitations are selected out for the discrete process in the hybrid model. In both models the Mott cross section and the Gryzinski cross section are used for elastic collisions and ionizations, respectively. The exact film/substrate boundary condition is considered. The characteristic and continuum fluorescence corrections are also included in the simulation. The simulation results agree well with experimental ones measured with a quartz oscillator. Effects of the introduction of the discrete energy loss process and the fluorescence correction are discussed in comparison between simulation and experiment.

Quantitative WDXS Microanalysis of Bismuth-Based BaBi 4 Ti 4 O 15 Perovskites Doped with Nb and Fe

Quantitative electron-probe microanalysis was used to determine the chemical composition of an Fe- and Nb-doped bismuth-based BaBi4Ti4O15 perovskite compound. Elemental concentrations of Fe, Nb, Bi, Ba and Ti were accurately measured using wavelength-dispersive X-ray spectroscopy that was optimised for the analysis of a complex oxide matrix containing minor concentrations of dopants. Measurements were performed with a JEOL JXA 840A electron probe microanalyser at 20 and 26 kV, 50 nA beam current, 100 s maximum counting time and 0.3% preset counting deviation (σc) using both PET and LiF crystals. K-ratios were quantified by the ZAF and the φ(ρz) PAP matrix-correction procedures. The results showed that dopants incorporate into the BaBi4Ti4O15 at Ti4 + sites according to the Ba1−4XBi4 + 4XTi4−4XFe4XO15 and Ba1 + 4XBi4−4XTi4−4XNb4XO15 solid-solution formulae. The majority of the excess charge introduced by the substitution of Ti4 + with Fe3 + or Nb5 + is compensated for the change in the Ba2 + /Bi3 + ratio.

Minimizing Errors in Electron Microprobe Analysis.

Errors in quantitative electron microprobe analysis arise from many sources including those associated with sampling, specimen preparation, instrument operation, data collection, and analysis. The relative magnitudes of some of these factors are assessed for a sample of NiAl used to demonstrate important concerns in the analysis of even a relatively simple system measured under standard operating conditions. The results presented are intended to serve more as a guideline for developing an analytical strategy than as a detailed error propagation model that includes all possible sources of variability and inaccuracy. The use of a variety of tools to assess errors is demonstrated. It is also shown that, as sample characteristics depart from those under which many of the quantitative methods were developed, errors can increase significantly.

The Al-Er-Mg ternary system Part I: Experimental investigation

Investigation of phase equilibria in the ternary system Al-Er-Mg has been carried out by means of differential thermal analysis (DTA), powder x-ray diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), and quantitative electron probe microanalysis (EPMA). The isothermal section at 400 °C has been established. An extended homogeneity region with Al substitution for Mg at a constant Er content has been found for (Mg1−x Al x )Er (0≤x≤0.78); a few other boundary binary phases give lower ternary solubility. A ternary compound, τ, of Al66.7Er10Mg23.3 stoichiometry, has been found to exist in the isothermal section at 400 °C.

Thermophysical properties of the system Al2O3 - MgO

Dense samples of two different magnesia spinels and alumina spinel and magnesia spinel composites were prepared by powder metallurgy techniques and characterised by quantitative metallography, x-ray, and electron microprobe analysis. For four kinds of pure spinels, the thermal conductivity, λ, was determined from thermal diffusivity data measured together with heat capacity and thermal expansion. Up to about 1000 K, thermal resistivity, 1/λ, of the spinels follows the relationship A + BT, and then becomes more or less temperature dependent. Three stoichiometric spinels show the same value of B, (14.4 ′ 0.2) × 10 - 5 m W - 1 , while the nonstoichiometric compound (Mg 0 . 8 5 Al 0 . 1 5 )Al 2 O 4 has B of 10.6 × 10 - 5 m W - 1 . The composites of the alumina-rich compositions at low temperatures obey the mixing rule. This is not the case for the magnesia-rich side of the phase composition. The high-temperature thermal conductivity function of the composites shows very complex behaviour.

Ionization Cross Sections for Quantitative Electron Probe Microanalysis

Quantitative procedures in electron probe microanalysis (EPMA) require the knowledge of various atomic parameters, the most fundamental of which is the ionization cross section. A number of semi-empirical, approximate analytical formulas have been proposed to calculate the ionization cross section. The simplicity of these formulas makes them suitable for quantitative EPMA procedures. However, it is difficult to assess their reliability because of the lack of accurate experimental data. Indeed, inspection of currently available data reveals that they are still scarce for many elements and, when they are available, one usually finds significant discrepancies between data from different authors. Fortunately, the inaccuracies in the semi-empirical cross section formulas used in EPMA have only a small effect on the analytical results when standards are used. Nonetheless, in quantitative EPMA studies at low overvoltages or using standardless methods, the evaluated compositions largely depend on the adopted ionization cross sections and, therefore, knowledge of accurate ionization cross sections is a requisite for the development of improved quantification methods.

Infrared and Raman spectra of Ga 2O 3–P 2O 5 glasses

The structure of x Ga 2 O 3(1−x) P 2 O 5(0.15 ⩽ x ⩽ 0.4) glasses is studied by infrared (IR) and Raman spectroscopy. The results of quantitative electron microprobe analysis reveal that two sets of glasses are formed with compositions corresponding to the gallium meta and pyrophosphates. Crystalline Ga(PO 3) 3 metaphosphate is also obtained and its IR and Raman spectra recorded in order to examine the spectral differences glass → crystal. The IR spectra of metaphosphate glasses show bands at 1250, 930, 775 and 485 cm −1 which, are assigned to the ν asPO 2, ν asPOP, ν sPOP and δPO 2 modes of the metaphosphate chain. In the Raman spectra are found patterns due to symmetric modes of PO 2 terminal and POP bridging bonds as well as features due to vibrations of GaO 4 tetrahedra and Ga–O–P bridges. Comparisons of the spectra of glasses with those of the crystal indicate that the interaction of Ga with the polyphosphate anions is more covalent in the glasses. The bands observed in the spectra of pyrophosphate glasses provide evidence for the involvement of ortho-, pyro- and polyphosphate groupings in the glass structure. The Raman spectra of both sets of glasses display intense low frequency bands, which we assigned to a symmetric bending of Ga–O–P bridging bonds involving four-coordinated gallium atoms. It is concluded that structure of Ga 2O 3–P 2O 5 glasses is a highly polymerized network consisting of a variety of phosphate anions cross-linked by GaO 4 tetrahedra. This account on glass structure is consistent with the great glass forming ability of the compositions studied.

Constitution, structural chemistry and magnetism in the ternary system Ce–Ag–Si

Phase relations were established for the Ce–Ag–Si system at 850°C by means of X-ray diffraction, light optical microscopy and quantitative electron probe microanalysis. Phase equilibria are characterised by the existence of extended solid solutions starting from the binaries: Ce(Ag x Si 1− x ) 2− y (ThSi 2-type), Ce(Ag 1− x Si x ) 1− y (unknown structure type) and Ce(Ag 1− x Si x ) 2− y (unknown structure type). Three ternary phases were found to exist, CeAg 2Si 2 (ThCr 2Si 2-type), Ce(Ag x Si 1− x ) 2− y (AlB 2-type) and the new ternary compound CeAgSi 2 with unknown structure type. Magnetic behaviour was studied from magnetic susceptibility and magnetisation measurements down to 1.7 K and employing magnetic fields up to 5 T. Soft ferromagnetism is observed for CeAg x Si 2− x (AlB 2-type) below 5 K. Alloys Ce(Ag x Si 1− x ) 2− y with 0.08< x Ag<0.30 (ThSi 2-type) encounter ferromagnetic order below 7 K. For x Ag=0.31 the ferromagnetic interaction changes to antiferromagnetism with T N=5.7 K. For CeAgSi 2 ferrimagnetic or canted antiferromagnetic order is indicated below 7 K.

Miscibility of binary VC–MC carbides in quaternary Fe–V–M–C alloys

A series of quaternary (Fe, V, M, C) alloys with different additions (Ti, Zr, Nb, Ta, Mo and W) were prepared. The phases were characterised by scanning electron microscopy. Quantitative electron probe microanalysis was used to analyse the carbides. As in ternary systems, MC x carbides formed in quaternary alloys are carbon deficient. TiC and VC formed a continuous solid solution, while Zr, which belongs to the same group, showed a solubility below 0.1% Zr in VC and V is less than 1% in ZrC. VC–TaC and VC–NbC formed a continuous solid solution at high temperature, but decomposed during cooling. In the presence of Mo, continuous variations of M and C levels are observed between VC and Mo 2C, while in the presence of W, the formation of an intermediate carbide of M 6C type limits the solubility of W in VC.

Effect of Cu and Zn on the melting and transformation temperatures of Pr and Gd

Phase equilibria in the R-rich regions of the R-Cu and R-Zn binary systems (R=Pr and Gd) have been investigated by differential thermal analysis, X-ray powder diffractometry, metallographic analysis and quantitative electron probe microanalysis. In these regions, the lowering (Δ T) of the melting and transformation temperatures of the rare earth metals by addition of copper and zinc resulted in eutectic and catatectic or eutectoidal type reactions. The Δ T observed in these systems are discussed and compared with those reported in the literature for the binary systems of Pr and Gd with Mg and with the elements from the 9th to the 14th group of the Periodic Table. In order to complete this systematics, a few Pr-rich Pr–Cd alloys have also been prepared and analysed.

Minimizing Errors in Electron Microprobe Analysis

Abstract Errors in quantitative electron microprobe analysis arise from many sources including those associated with sampling, specimen preparation, instrument operation, data collection, and analysis. The relative magnitudes of some of these factors are assessed for a sample of NiAl used to demonstrate important concerns in the analysis of even a relatively simple system measured under standard operating conditions. The results presented are intended to serve more as a guideline for developing an analytical strategy than as a detailed error propagation model that includes all possible sources of variability and inaccuracy. The use of a variety of tools to assess errors is demonstrated. It is also shown that, as sample characteristics depart from those under which many of the quantitative methods were developed, errors can increase significantly.

Post-magmatic Remobilization of Platinum-Group Elements in the Kelly Lake Ni-Cu Sulfide Deposit, Copper Cliff Offset, Sudbury

Pyrrhotite, chalcopyrite, and pentlandite are the dominant sulfide minerals in the 740 zone of the Kelly Lake orebody (Inco Ltd.), Copper Cliff Offset, Sudbury. Petrographic and quantitative electron microprobe analyses of minerals, from sulfide assemblages and host quartz diorite, of the 740 deposit have revealed three processes that have affected sulfide mineralization and associated sulfarsenide and platinum-group-mineral (PGM) distribution: magmatic, hydrothermal, and tectonic. Accessory, zoned cobaltite, and gersdorffite occur in sulfides as a result of these three processes, and PGM occur dominantly in hydrothermally remobilized and deformed ores. Where PGM are present in sulfarsenides they provided nuclei for sulfarsenide growth. Solitary PGM are orders of magnitude larger than those PGM found within sulfarsenide minerals. Five varieties of PGM occur, michenerite and sperrylite being the most common, with lesser froodite, hollingworthite, and ruarsite. The effect of a deformation is a localized fabric in the ore, revealed by pyrrhotite and chalcopyrite bands; pentlandite porphyroblasts also partially define the foliation. The deformed ore is also characterized by alteration of the adjacent quartz diorite, which produced an alteration assemblage including almandine garnet, Fe-rich biotite, and chlorite.

Characterisation of mineralogical forms of barium and trace heavy metal impurities in commercial barytes by EPMA, XRD and ICP-MS.

This study was carried out to characterise the mineralogical forms of barium and the trace heavy metal impurities in commercial barytes of different origins using electron probe microanalysis (EPMA), X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). Qualitative EPMA results show the presence of typically eight different minerals in commercial barytes including barite (BaSO4), barium feldspar, galena (PbS), pyrite (FeS2), sphalerite (ZnS), quartz (SiO2), and silicates, etc. Quantitative EPMA confirms that the barite crystals in the barytes contain some strontium and a little calcium, whereas trace heavy metals occur in the associated minerals. Analysis of aqua regia extracts of barytes samples by ICP-MS has shown the presence of a large number of elements in the associated minerals. Arsenic, copper and zinc concentrations correlate closely in all 10 samples. The findings suggest that barytes is not, as traditionally thought, an inert mineral, but is a potentially toxic substance due to its associated heavy metal impurities, which can be determined by an aqua regia digest without the need for complete dissolution of the barite itself. X-ray powder diffraction was not informative as the complex barite pattern masks the very weak lines from the small amounts of associated minerals.

Quantitative electron probe microanalysis of oxygen in compounds with pentavalent vanadium: an ultrastrong absorption phenomenon

Electron probe microanalysis of oxygen in vanadium compounds gives values which are substantially smaller then the actual oxygen content. By measuring the intensity of the O Kα line in V2O5 the absorption coefficient of V was found to be 51 000 cm2 g−1, which is much higher than the corresponding values from commonly accepted sources. To explain this phenomenon, we suggest selective absorption of the O Kα line by the strong white line of the absorption spectrum of pentavalent vanadium. Copyright © 2000 John Wiley & Sons, Ltd.

Petrography, mineralogy and geochemistry of the Zarshuran Carlin-like gold deposit, northwest Iran

Gold mineralisation at Zarshuran, northwestern Iran, is hosted by Precambrian carbonate and black shale formations which have been intruded by a weakly mineralised granitoid. Granitoid intrusion fractured the sedimentary rocks, thereby improving conditions for hydrothermal alteration and mineralisation. Silicification is the principal hydrothermal alteration along with decalcification and argillisation. Three hydrothermal sulphide mineral assemblages have been identified: an early assemblage of pyrrhotite, pyrite and chalcopyrite; then widespread base metal sulphides, lead-sulphosalts and zoned euhedral arsenical pyrite; and finally late network arsenical pyrite, massive and colloform arsenical pyrite, colloform sphalerite, coloradoite, and arsenic–antimony–mercury–thallium-bearing sulphides including orpiment, realgar, stibnite, getchellite, cinnabar, lorandite and a Tl-mineral, probably christite. Most of the gold at Zarshuran is detectable only by quantitative electron microprobe and bulk chemical analyses. Gold occurs mainly in arsenical pyrite and colloform sphalerite as solid solution or as nanometre-sized native gold. Metallic gold is found rarely in hydrothermal quartz and orpiment. Pure microcrystalline orpiment, carbon-rich shale, silicified shale with visible pyrite grains and arsenic minerals contain the highest concentrations of gold. In many ways Zarshuran appears to be similar to the classic Carlin-type sediment-hosted disseminated gold deposits. However, relatively high concentrations of tellurium at Zarshuran, evidenced by the occurrence of coloradoite (HgTe), imply a greater magmatic contribution in the mineralising hydrothermal solutions than is typical of Carlin-type gold deposits.

Quantitative Electron Probe Microanalysis of Boron

Quantitative electron probe microanalysis of boron has been performed in 28 binary borides in the range of 4–30 kV. In principle, intensity measurements of ultra-light element radiations can only be performed correctly if the effects of peak shifts and peak shape alterations between specimens and standard are taken into account. The analysis of boron is further complicated by the fact that the peak shape may also be dependent on the crystallographic orientation of the specimen with respect to the electron beam and spectrometer. This was found to be the case in 50% of the compounds investigated. However, if the measurements are performed properly, and if a good matrix correction program is used in conjunction with a consistent set of mass absorption coefficients, it is possible to obtain a narrow error distribution. The final histogram, displaying the number of analyses versus the ratio between calculated and measured intensity ratios that we obtained for 192 analyses with our PROZA96 program, had a root-mean-square value of 3.31% and a mean value of 1.0022.

Development of a Spectral Database for Testing Quantitative Electron Probe Microanalysis of Rough, Bulk Samples

Abstract The vast majority of applications of electron probe x-ray microanalysis takes place on specimens which deviate significantly from the ideal configuration. Classic quantitative x-ray microanalysis makes the tacit assumption that the only reason the unknown differs in emitted x-ray intensity from standards is that there is a difference in composition between them. While this seems trivial, it forces the analyst to eliminate a major non-compositional source of possible intensity differences, namely the geometric effects associated with surface roughness. An important early paper by Yakowitz demonstrated that deviations from an ideal flat surface due to surface topography could seriously degrade the accuracy of analysis. Yakowitz interrupted the grinding and polishing procedure on pure elements and alloys at various stages and measured the variance in the x-ray intensity as the probe was scanned across the surface as compared to the predicted distribution based on counting statistics.

Useful Lead and Bismuth Standards for Quantitative Electron Probe Microanalysis

Abstract Lead and bismuth standards for quantitative electron probe microanalysis have always been a problem due to mechanical polishing and surface oxidation upon atmospheric exposure. Some Pb and Bi compounds, such as the selenides and tellurides, can be obtained commercially as solid pieces that are large enough to be mounted as useful standards, but they can also form non-stoichiometric solid solutions. This paper is a description of the initial work done on the testing of some selenides and tellurides to evaluate their usefulness as standards for quantitation. In addition, improved procedures for preparing the Pb and Bi element and compound specimens are being used to reduce surface oxidation. Primarily Pb samples were evaluated here, but the project will be extended in the future to include more Bi materials. Experimental Most specimens were mounted in silver epoxy in multi-element mounts that were repolished according to the description below. Additional specimens of PbTe, PbSe, and Pb were mounted in epoxy for this work.

Response to “Comment on ‘Electron microprobe quantification: A new model based on electrons rather than on mass’ ” [J. Appl. Phys. 87, 8220 (2000)

Fundamental physical law informs that neutrons play no role in electron probe microanalysis, and therefore, mass-based models follow an improper route to data reduction. Castaing’s mass-based first approximation inappropriately remains the starting point—see any microprobe textbook—for development of quantitative electron probe microanalysis. By incorrectly relating intensity of characteristic x rays to mass rather than to charge, such conventional models demand an isotope (mass) effect; our robust experiments detected none.

Quantitative electron probe microanalysis of oxygen in compounds with pentavalent vanadium: an ultrastrong absorption phenomenon

Electron probe microanalysis of oxygen in vanadium compounds gives values which are substantially smaller then the actual oxygen content. By measuring the intensity of the O Kα line in V2O5 the absorption coefficient of V was found to be 51 000 cm2 g−1, which is much higher than the corresponding values from commonly accepted sources. To explain this phenomenon, we suggest selective absorption of the O Kα line by the strong white line of the absorption spectrum of pentavalent vanadium. Copyright © 2000 John Wiley & Sons, Ltd.