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R. Jenkins
Chemistry
English
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Book
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Chapter
Estimation of Error Introduced by Ignoring the Background
Whenever X-ray intensity measurements are made on a selected peak, occuring at a certain setting of the goniometer, some fraction of the measured counting rate is always due to background. The significance of ...
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Variation of limit of detection with analysis time
A series of measurements of fluorine in cement sample yielded a peak counting rate of 4 c/s/% for fluorine (F Kα) over a background of 6.5 c/s.
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Continuous radiation — Scattered radiation
A The continuous radiation from an X-ray tube is scattered by the sample, diffracted by the analyzing crystal and measured by the detector.
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Particle statistics in X-ray diffractometry
Only those crystallites having the reflecting planes almost parallel to the specimen surface can contribute to a certain reflection. The intensity of the resulting diffraction is thus dependent on this number ...
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Dispersion as a function of ‘d’ spacing
LiF is commonly used as an analysing crystal. The (200) reflection planes are commonly used, having a “2d” value of 4.028 Å. It is, however, possible to use reflecting planes with other Miller indices (hkl) for e...
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Determination of CaO in cement (ratio measurement)
The following data were obtained using a series of cement samples. Counting ratios were determined on the Ca Kα line using sample 5 as the ratio standard.
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Absorption correction involving primary and secondary absorption
The slope of a calibration curve for a certain element is dependent upon the total absorption of the measured wavelength within the sample matrix. Although it is common practice to assume that only secondary a...
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Pulse height selection — crystal fluorescence
It is necessary to set up an X-ray spectrometer for the measurement of sodium in a series of rock specimens. An argon/methane flow counter is being employed and a KAP (potassium hydrogen phthalate) analysing ...
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Calculation of matrix absorption and prediction of absorption effects
The total secondary absorption of a matrix is given by
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Chapter
Calculation of quantity of heavy absorber needed to minimize matrix effects
In the analysis of tin ores it is found that a very curved calibration line is obtained due to the large difference in the mass absorption coefficients of the two matrix components Sn (µ = 13) and SiO2 (µ = 1.80)...
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Use of α correction factors (concentration correction)
A series of samples are being analysed for lead using the Pb Lα line. It is found that zinc which is also present strongly absorbs the Pb Lα wavelength resulting in a very poor calibration curve. The following da...
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Quantitative diffractometry — determination of Anatase in Rutile
A sample is known to contain two crystalline modifications of TiO2, namely rutile and anatase. Spectrographic analysis failed to reveal the presence of other elements, so the sample can be assumed to consist only...
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Determination of dead time
It is necessary to determine the dead time of an X-ray spectrometer using the Kβ/Kα counting ratio method. The following data were obtained on the Kα and Kβ lines of tin by varying the X-ray tube current and keep...
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Estimation of expected intensities in mixtures
The intensity of the 3.34 Å line of α-quartz (SiO2) has to be estimated in a mixture consisting of 10% α-quartz and 90% CaSiO3. Nickel filtered Cu Kα radiation is used. The intensity of the 3.34 Å line in pure α ...
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Measurement of coating thickness on irregular shaped objects
The thickness of Cr plating on a piece of iron of rather irregular but flat shape has to be measured.
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Use of primary filters for removal of characteristic tube lines
It is necessary to measure low concentrations of chromium using a spectrometer equipped with a chromium anode X-ray tube. A titanium filter can be fitted over the tube window to minimize the intensity of the Cr K
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Choice of detectors
A choice has to be made between the scintillation counter and the flow proportional counter for the measurement of a certain wavelength.
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Utilization of the ß filter and pulse height selector in diffractometry
A filter is very often used in X-ray diffractometry to reduce the background level and the intensity of β-radiation. This filter can be placed either between X-ray tube and specimen or between the specimen and de...
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Chapter
Dispersion of the diffractometer
The dispersion of the diffractometer (dθ/dλ) can be expressed in the given form obtained by differentiating the Bragg law nλ = 2dsinθ
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