JP3610256B2 - X-ray fluorescence analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluorescent X-ray analyzer that irradiates a sample with X-rays and measures the fluorescent X-rays emitted from the sample to determine the content of elements constituting the sample.
[0002]
[Prior art]
FIG. 1 is a diagram showing a configuration of an energy dispersive X-ray fluorescence analyzer. High-speed electrons collide with the X-ray tube 2, which is a kind of vacuum tube, from the high-voltage power supply 1 for the X-ray tube, and the generated primary X-ray is irradiated onto the sample 3. The energy distribution of X-rays generated at this time is a distribution in which characteristic X-rays corresponding to the target material are superimposed on continuous X-rays as shown in FIG. Various fluorescent X-rays are generated from the sample 3 and detected by the semiconductor detector 4. A voltage is applied to the semiconductor detector 4 from a high-voltage power supply 5 for the detector. The output of the semiconductor detector 4 has a staircase waveform, indicating that each step of the staircase detects X-rays, and the height of each step indicates the wavelength, that is, energy. The pulse processor 6 converts each step of the staircase into a pulse proportional to its height, and the ADC 7 converts the height into digital data for each pulse. When one pulse is converted, 1 is added to the position corresponding to the height of the pulse in the data memory 8, and as a result, a spectrum indicating the fluorescent X-ray energy on the horizontal axis and the quantity on the vertical axis is generated. The system 9 reads out the contents and performs qualitative analysis and quantitative analysis for display.
[0003]
FIG. 3 is a diagram showing spectrum data when stainless steel (sus304) is measured. The horizontal axis corresponds to energy, and the vertical axis corresponds to the element content. On the other hand, the energy and intensity of fluorescent X-rays peculiar to each element are stored in a database in advance in the computer. By comparing with the spectrum data of FIG. It is possible to determine and identify the elements contained in the sample. For example, in the spectrum of FIG. 3, it can be seen that the strongest peak is at 6.4 keV, and when 6.4 keV fluorescent X-rays are examined from the database, it can be seen that it is Kα ray among Fe fluorescent X-rays.
[0004]
After performing qualitative analysis in this way, quantitative analysis of how much the element is contained is performed. When calculating the intensity of an element subjected to qualitative analysis, an upper limit and a lower limit of spectrum energy may be designated and values within that range may be integrated. However, in practice, there is a background, and the fluorescent X-rays may overlap each other, and thus cannot be simply obtained. For example, in FIG. 3, CrKβ is actually overlapped with MnKα, and MnKβ is overlapped with FeKα.
[0005]
When the fluorescent X-rays overlap with each other in this way, an accurate integrated intensity is calculated using a database obtained by measuring the pure spectrum of each element and performing a comparison operation with this database. For example, in FIG. 4, when FeKα and MnKβ are overlapped, if the respective pure spectra are FeKαp and MnKβp, FeKα is
FeKα = A × FeKαp + B × MnKβp (1)
It can be expressed as Since this relationship is established for each energy point in the spectrum of FIG. 4, the constants A and B are obtained by obtaining the equation (1) for a plurality of points and solving this, and as a result, a pure spectrum can be obtained. Yes, quantitative analysis is performed.
[0006]
[Problems to be solved by the invention]
By the way, in the energy dispersive X-ray analyzer shown in FIG. 1, the primary X-ray includes continuous X-rays, and the obtained spectral data includes Bragg conditions other than the fluorescent X-rays emitted from the sample. Diffracted X-rays satisfying the above conditions are included, which causes deterioration in accuracy of qualitative analysis, accuracy of quantitative analysis, and quantitative reproducibility.
[0007]
In order to avoid the inclusion of diffracted X-rays in the detected fluorescent X-rays, for example,
(1) Monochromatic primary X-rays.
(2) Change the incident angle to the sample and the extraction angle.
Etc. can be considered. However, although the measure (1) is useful, it is necessary to add a mechanism for that purpose, so the apparatus becomes large, the X-ray path is long, and only a certain wavelength is extracted, so the X-ray intensity is greatly reduced. In order to compensate for this, the intensity of the X-ray source must be increased several times to several tens of times, and the size and cost of the apparatus cannot be avoided. Regarding (2), since the wavelength at which the diffracted X-rays are emitted differs depending on the sample, it is necessary to set the incident angle and the extraction angle at arbitrary positions, but it is still inevitable to increase the size and cost of the apparatus.
[0008]
An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to easily remove diffracted X-rays by software and improve qualitative analysis accuracy, quantitative analysis accuracy, and quantitative reproducibility.
[0009]
[Means for Solving the Problems]
The present invention irradiates a sample with X-rays, detects fluorescent X-rays emitted from the sample with an energy dispersive detector, and measures the content of elements constituting the sample from the detected spectral data. The analyzer has a fluorescent X-ray spectrum database and a diffracted X-ray spectrum database obtained by measuring in advance with a standard sample, and for the measured fluorescent X-ray spectrum data, the fluorescent X-ray spectrum database and the diffracted X-ray spectrum database. And an analysis processing means for calculating a fluorescent X-ray spectrum by comparing and separating the overlap of fluorescent X-rays and the overlap of fluorescent X-rays and diffracted X-rays.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
FIG. 5 is a block diagram showing the apparatus configuration of the X-ray fluorescence analyzer of the present invention. The fluorescent X-ray detector 11 irradiates the sample with X-rays and detects X-rays generated from the sample. The analysis processor 12 refers to the fluorescent X-ray spectrum database 13 and the diffracted X-ray spectrum database 14 obtained in advance for the standard sample, and evaluates and analyzes the overlap between the fluorescent X-rays and the overlap with the diffracted X-rays from the detected spectrum. It has a function to calculate a pure spectrum.
[0011]
For example, assuming that spectrum data as shown in FIG. 6 is obtained, peaks (1) to (4) are fluorescent X-ray peaks, and (5) is diffraction X-rays. (1) to (3) The intensity of is used as it is as data representing the amount of the element, but the peak of (4) is accompanied by an error due to the influence of (5). If the peak of (5) is always constant, the error can be taken into account, but the intensity of the same sample is also affected by the position where the primary X-ray strikes and the in-plane rotation position of the sample. Often changes. As shown in FIG. 2, since the primary X-ray is a continuous X-ray, there is a high possibility that some wavelength satisfies the diffraction condition. If the sample is powder, it is presumed that diffraction lines of all crystal planes are emitted, and in a sample in which crystal grains are distributed, diffraction lines may or may not come out depending on the location.
[0012]
FIG. 7 is a diagram showing an example in which the overlap between a minute amount of Ti and diffraction lines in Al is measured by changing the sample position. In the example of FIG. 7, an example of measurement at five positions is shown, and it is clear from the intensity of the Al (1, 1, 1) diffraction line and Al (2, 2, 0) diffraction line that the sample position is clear. The strength changes greatly depending on the amount of TiKα and TiKβ, which makes it difficult to accurately analyze trace amounts of Ti.
[0013]
However, since the peak profile of the diffracted X-ray (5) itself does not change, this is stored as the diffracted X-ray spectrum database 14 and compared with this data, the diffracted X-ray (5) is excluded and the fluorescent X-ray is accurately detected. It is possible to determine the intensity of the line. Therefore, in the present invention, by having the diffracted X-ray spectrum database 14, the diffracted X-ray spectra can be obtained by a method similar to the conventional method for evaluating the overlap of fluorescent X-rays using the fluorescent X-ray spectrum database. Remove strength. For example, as shown in FIG. 8, a standard sample of Al that does not contain Ti is measured in advance to obtain spectral data of diffraction lines and create a database. In the example of FIG. 7, the diffraction line of Al (2, 0, 0) and the fluorescent X-ray of TiKα overlap, and the following equation (2) similar to equation (1) is used to separate this. To do.
TiKα = A × TiKαp + B × Diffraction line (2, 0, 0) (2)
TiKαp is a pure spectrum, and A and B are constants. Since the equation (2) is established at each point where the diffraction lines and the fluorescent X-rays overlap, the constants A and B are obtained by solving these equations and solving these equations, whereby the diffraction X-rays are obtained. The X-ray fluorescence intensity from which is removed can be obtained.
[0014]
Strictly speaking, the conditions to which the present invention can be applied must be a sample in which the location where the diffracted X-rays appear is known in advance. Therefore, it is difficult to apply to completely unknown samples, but it is usually known in advance or easy to judge in management analysis such as quality control, and quantitative reproducibility is strongly required. It is most suitable for applying the present invention.
[0015]
【The invention's effect】
As described above, according to the present invention, in addition to the fluorescent X-ray spectrum database, the peak profile of diffracted X-rays is stored as a database, and when calculating the fluorescent X-ray intensity, the fluorescent X-rays are referenced with reference to these databases. Since the overlap and the contribution of diffracted X-rays can be removed, the intensity of fluorescent X-rays can be accurately calculated, and the quantitative accuracy and reproducibility can be dramatically improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a conventional energy dispersive X-ray fluorescence spectrometer.
FIG. 2 is a diagram showing an energy distribution generated in an X-ray tube.
FIG. 3 is a diagram showing spectral data when stainless steel is measured.
FIG. 4 is a diagram illustrating a method for separating the overlap of fluorescent X-rays.
FIG. 5 is a block diagram showing an apparatus configuration of a fluorescent X-ray analyzer according to the present invention.
FIG. 6 is a diagram showing an example of spectral data having an overlap with diffracted X-rays.
FIG. 7 is a diagram showing an example in which the overlap between a trace amount of Ti in Al and a diffraction line is measured by changing the sample position.
FIG. 8 is a diagram showing spectral data of diffraction lines of an Al standard sample not containing Ti.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... X-ray fluorescence detection apparatus, 12 ... Analysis processing apparatus, 13 ... X-ray fluorescence spectrum database, 14 ... Diffraction X-ray spectrum database

Claims (1)

In a fluorescent X-ray analyzer that irradiates a sample with X-rays, detects fluorescent X-rays emitted from the sample with an energy dispersive detector, and measures the content of elements constituting the sample from the detected spectral data. Having a fluorescent X-ray spectrum database and a diffraction X-ray spectrum database obtained by measuring in advance with a standard sample, with respect to the measured fluorescent X-ray spectrum data, refer to the fluorescent X-ray spectrum database and the diffraction X-ray spectrum database; A fluorescent X-ray analyzer characterized by comprising an analysis processing means for calculating and calculating a fluorescent X-ray spectrum by comparing and separating overlapping of fluorescent X-rays and overlapping of fluorescent X-rays and diffracted X-rays.

Images