JPH0484743A - Quantitative analysis method using X-ray spectroscopy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an analytical method for performing elemental quantitative analysis by spectroscopy of X-rays emitted from a sample when the sample is irradiated with excitation radiation.

(Prior Art) When a sample is irradiated with an excitation beam such as an electron beam, continuous xn and characteristic X-rays of the elements constituting the sample are emitted from the sample. For quantitative elemental analysis of a sample, it is necessary to measure the characteristic X-ray intensity of each element emitted from the sample, but in this case, continuous X-rays form the background of the characteristic X* peak of the sample component elements. In order to measure the characteristic X-ray intensity of a component element, it is necessary to determine the background intensity at the characteristic X-ray wavelength position in advance.

For this reason, in the past, wavelength scanning was performed in an appropriate wavelength range before and after the characteristic X-ray wavelength of the component element to be quantified using an X-ray spectrometer, and the background region before and after the rise and fall of the characteristic X-ray peak was A method has been used in which the radiation intensity is measured and the background intensity at a characteristic X-ray wavelength position is determined by interpolation. However, with this method, it is necessary to perform X-ray measurements at wavelengths other than the characteristic X-ray wavelength of the element to be quantified, so there are problems in that the analysis takes time and the problem that only one characteristic X-ray peak X&! on both sides! When estimating the background at the characteristic Xv1 position from the measurement results, if the slope of the background is steep or curved, the accuracy of this estimation will be low, and the X-ray spectrum is complex and the X-ray peak When the peaks are close to each other, there is a problem that the background itself at a position away from the peak center cannot be accurately determined.

(Problem to be solved by the invention!!) The present invention only performs X-ray measurement at the characteristic X-ray wavelength position of the component elements of the sample, and separately performs wavelength scanning with an X-ray spectrometer for background measurement. The present invention aims to provide an X-ray spectroscopic analysis method that can perform elemental quantification based only on the measured value of the characteristic X-ray wavelength position of the measured sample component element.

(Means for solving the problem) For each element, select a plurality of standard samples that do not contain that element from among the standard samples listed above and measure the X-ray intensity at the characteristic X-ray wavelength position of that element. From the measured X-ray intensity and the average atomic number of the standard sample used for measurement, create a relationship curve between the X-ray intensity and average atomic number at the characteristic X-ray wavelength position of each element. Then, obtain a first approximation of the elemental composition of the sample from the xm measurement value at the characteristic X-ray wavelength position of each component element for the sample to be measured, and calculate the average atomic number of the sample from this first approximation composition. , the background at the characteristic X-ray wavelength position of each component element is determined from the above relationship curve, the second approximate elemental composition is determined by the value obtained by subtracting the above background from the measured value at the characteristic X-ray wavelength position of each element, and this The background at each elemental characteristic X-ray position was determined again from the elemental composition of the second approximation, and the same operations as described above were repeated to successively approximate the elements in the sample to be measured.

(Function) When quantifying elements by X-ray spectroscopy, continuous X-rays constitute the background of characteristic X-ray peaks of each component. Continuous wLX-rays are emitted when electrons incident on a sample are repelled and accelerated by the extranuclear electrons of atoms constituting the sample, so the formation of the spectrum of continuous X-rays depends on the number of incident electrons. Energy is related to the number of extranuclear electrons of the elements that make up the sample, that is, the atomic weight. Average atomic number Zm
is given by the following, where Wffi is the weight percent of the sample component element, Mi is the atomic weight, and Zi is the atomic number. A. The elements that make up the sample now.

B,...N, standard samples containing one of these elements and having different element combinations and compositions are (B, C
...N) Multiple types that do not contain A.

(A, C,...N) Multiple types that do not contain B.

(A, B,...M) Multiple types that do not contain N.

That's what I come to say. This is an example of how to combine elements.
The point is to have a plurality of standard samples for each component element that contain each element as much as possible but do not contain one of each component element. In this way, the X-ray measurement value at the characteristic X-ray wavelength position of a sample that does not contain any element is based on the background at that wavelength, since the characteristic X-ray of that element does not exist. However, this varies depending on the elemental composition, so by calculating the average atomic number of those standard samples, the relationship curve between the background intensity at the characteristic X-ray wavelength position and the average element number can be obtained. .

In the method of the present invention, the background at the characteristic X-ray wavelength position of one element cannot be determined unless the average atomic number of the sample is known, and the relationship between the average atomic number and the average atomic number cannot be determined unless the elemental composition of the sample is known. First, we calculate the first approximate elemental composition from the characteristic X-ray intensity of each element measured by the sample, calculate the average atomic number, calculate the background, and then determine the elemental composition by successive approximations. be.

(Example) The table below shows an example of the composition of a standard sample. The component elements of these standard samples are A, B, ...N, which are the same as the component elements of the sample to be measured. In the case of capacity analysis for products that have been tested, these component elements are known. In the table below, 1°2, . . . a in the upper column is the number of the standard sample, and the numbers in the table are the weight % of each element.

1234567=-a A 50.1 1.2 0 1.8 0 9.2
1.8... On O44,21,012,800
0... 5.2 CIo, 8 5.0 0 0 6
3.2 0 0 ... 3.8D O23,22
-210,10018... 3.2 When calculating the relationship curve between background and average atomic number at the characteristic X-ray wavelength position for an element using the standard sample in the above table, element A in the above table is not included. Select the standard sample This is the sample number 3.5.
...a, and these standard samples have different element combinations and composition ratios, so the average atomic number is different. In these standard samples, there is no X-ray peak at the characteristic X-ray wavelength position of element A, and the constant value I on the X-ray side for each sample is
If you plot the and average atomic number, it will look like Figure 1, and find the equation of the curve connecting these points using the method of least squares,
Characteristic Xt of element A is a relational expression between the background intensity at the 8 wavelength position and the average atomic number. Similarly, for other elements, find the relational expression between the background intensity and the average atomic number (. Also, create a calibration curve for each element using the standard samples in the table above. To create,
Using the standard sample containing element A, sample number 1 in the table above, calculate the X-ray intensity at the characteristic X-ray wavelength position of element A!
element A, which is determined by the above-mentioned method, by measuring a.
Using the relational expression between the background and the average atomic number,
From the average atomic number of the standard sample of sample number 1, the characteristics of element A in this sample) Background intensity at wavelength ■
~Ask for it! Since the value subtracted from a is the characteristic X-ray intensity for a 50.1% concentration of element A, a calibration curve is created using this. Similarly, for element B, sample number 2
Create a calibration curve using the standard sample. Standard samples with the underlined component amounts in the table above are used to create a calibration curve for that component element. Of course, it is not prohibited to use these standard samples to determine the relational expression between the background of other elements and the average atomic number. In this way, the relational expression between the background intensity and the average atomic number for each component element,
Once the calibration curve is determined, the results are stored in the computer's memory and the sample to be measured is quantitatively analyzed. FIG. 2 is a flowchart of this quantitative analysis operation. First, regarding the sample to be measured, the characteristics X of each component element A, B,...N
X-ray intensity at line wavelength position 1 u na , I u n
b, ・- is measured (a). Next, the first approximate concentrations Wal, Wbl, . . . of each component element are determined by fitting the above X-ray intensities to the calibration curve of each element. That is, in this case, the first approximation is one in which the intensity of each component is determined without background correction, but the method of determining the first approximation is not limited to this. If the approximate ratio between each component is predicted in advance, calculate the average atomic number based on it, or if there is no particularly abundant or rare element between each component, it is possible to calculate the average atomic number based on it. It is also possible to calculate the average atomic number assuming that the components are mixed, perform background correction, and then determine the ratio of each component using each calibration curve. Once the first approximation is determined, the average atomic number of the sample to be measured is determined based on it (c), and the background of the characteristic X-ray wavelength position for each component is calculated from the relational expression between the background of each component element and the average atomic number. Determine the ground intensity and subtract it from Iuna, Iunb, etc. for each component (background correction) (d). Based on the results, determine the second approximate concentration of each component from each element calibration curve (e). Repeat the operations (c) to (e) by closing the results of e) again as Wa1, Wbl, etc., and when the difference between the previous Wal, etc. and the current Wal' becomes less than a predetermined minute value, The above-mentioned repetition is discontinued (g), and the ZAF correction value is calculated using the last Walo, Wb 1°, etc. (g). The ZAF correction calculation is performed because the characteristic Xwi intensity of the component elements is determined by the composition of the sample, the excitation efficiency of electrons etc. increases due to the influence of coexisting elements, the X-ray absorption effect of other elements is different, and the excitation by characteristic X-rays of other elements ( This calculation corrects the curvature of the calibration curve due to differences in fluorescence effects. Actual percentage of each component element determined in step (g)
W a2.

Wb2. ...etc., Wal, Wbl of step (c)
etc., repeat (c), (d), (e), and (g) (in this case, step (f) does not pass), Wa 2 + W
When the difference between b 2 , ..., etc. from the previous time becomes less than the allowable value, the repetition ends (ch), and the finally obtained Wa
2. Wb2. ... is the quantitative value of each element.

(Effect of the invention) According to the method of the invention, the X-ray spectrometer can
Since only the lines need to be measured, the time required for measurement can be significantly shortened compared to conventional methods that also measure the background intensity. Background can be accurately determined and quantified even in lines, improving analysis accuracy.

[Brief explanation of drawings]

Figure 1 shows X&! at the wavelength that corresponds to the average atomic number. FIG. 2 is a flowchart of data processing operations in an embodiment of the present invention. Agent Patent Attorney Kosuke Agata

Claims (1)

[Claims] Using multiple standard samples that do not contain one of the elements that make up the sample but have different combinations of elements and composition ratios,
For each element, select multiple standard samples that do not contain that element from among the standard samples listed above, measure the X-ray intensity at the characteristic X-ray wavelength position of that element, and compare the measured X-ray intensity with the measurement value. From the average atomic number of each standard sample used, create a relationship curve between the X-ray intensity at the characteristic X-ray wavelength position of each element and the average atomic number, and A first approximation of the elemental composition of the sample is obtained from the X-ray measurement value at the characteristic X-ray wavelength position, and the average atomic number of the sample is calculated from this first approximation composition. The background at the characteristic X-ray wavelength position is determined, and the second approximate elemental composition is determined by the value obtained by subtracting the background from the X-ray intensity measurement value at the characteristic X-ray wavelength position of each element. A quantitative analysis method using X-ray spectroscopy, characterized in that the background at each elemental characteristic X-ray position is determined again from , and the same operations as described above are repeated to successively approximate the elements in the sample to be measured.