JP2940810B2 - X-ray fluorescence analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluorescence analyzer for irradiating a sample with primary X-rays and analyzing generated X-ray fluorescence.

[0002]

2. Description of the Related Art In a conventional X-ray fluorescence spectrometer, for example, when analyzing carbon contained in a sample containing mainly iron (carbon steel, stainless steel, etc.), Ni is used as a spectroscopic element.
/ C artificial accumulation film is used.

[0003]

However, in such an analysis, although the sample does not actually contain carbon, it is detected that carbon is contained, or the sample is actually contained. Is detected as containing more carbon than that contained in the sample, that is, the SN ratio and the accuracy of the calibration curve are reduced. Although the cause was unclear, the present inventor has argued that, in the above case, the fluorescent X-ray Fe-Lα ray generated from iron in the sample excites carbon in the artificial cumulative film. To generate fluorescent X-rays C-Kα rays, which were found to be caused by incidence on the detector.

Accordingly, an object of the present invention is to provide a fluorescent X-ray analyzer having improved SN ratio and accuracy of a calibration curve.

[0005]

In order to achieve the above object, an X-ray fluorescence spectrometer according to claim 1 comprises an X-ray source for generating primary X-rays and a primary X-ray irradiated. The apparatus includes a spectroscopic element arranged in a path of a secondary X-ray generated from a sample and a detector on which the X-ray diffracted by the spectroscopic element is incident, and analyzes carbon in the sample. And, between the sample and the spectroscopic element in the passage of the secondary X-rays generated from the sample, a fluorescent X-ray generated from carbon in the sample is transmitted by being made of an organic compound mainly composed of carbon. And a filter that absorbs the secondary X-rays that excites carbon in the spectral element.

[0006]

According to the X-ray fluorescence spectrometer of the first aspect, the filter disposed between the sample and the spectroscopic element is composed of the constituent elements of the spectroscopic element among the fluorescent X-rays generated from the sample.
Since it absorbs short fluorescent X-ray wavelength than the absorption edge wavelength of carbons that may excite some carbon, excitation of the carbon in the spectral element is reduced, thereby improving the accuracy of the SN ratio and the calibration curve.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG.
The X-ray analyzer first includes an X-ray source 1 for generating a primary X-ray 2.
A sample stage 8 on which the sample 3 is fixed, and a spectroscopic element 5 which is an artificially accumulated Ni / C film disposed in a passage of fluorescent X-rays 4 generated from the sample 3 irradiated with the primary X-rays 2. And a detector 7 on which X-rays 6 diffracted by the spectral element 5 are incident. Then, between the sample 3 and the spectroscopic element 5 in the passage of the fluorescent X-rays 4 generated from the sample 3, an organic compound containing carbon as a main component, for example, polypropylene, preferably 0.3 μm or more and 0.9 μm in thickness The following filter 9, more preferably, having a thickness of 0.5 μm or more and 0.7 μm or less is arranged.

Here, in general, in an X-ray fluorescence analyzer, the incident angle of the secondary X-rays 4 generated from the sample 3 on the spectroscopic element 5 in order to continuously analyze the X-rays of fluorescence of a certain range. θ, an extension of the secondary X-ray 4 generated from the sample 3 (indicated by a two-dot chain line in FIG. 1), and an X-ray 6 diffracted by the spectroscopic element 5.
The spectroscopic element 5 and the detector 7 are rotationally scanned about the point of incidence of the secondary X-rays 4 on the spectroscopic element 5 while maintaining the relation of the spectroscopic angles 2θ formed by θ and 2θ respectively. Correspondingly, the filter 9 always exists between the sample 3 and the spectroscopic element 5 in the path of the secondary X-ray 4 generated from the sample 3 during this rotational scanning, and the X-ray diffracted by the spectroscopic element 5. It is attached to the spectroscopic element 5 at an appropriate angle and length so as not to interfere with the path of the line 6.

Next, the operation of this embodiment when analyzing the carbon contained in the sample 3 containing iron as a main component will be described. Primary X-rays generated from the X-ray source 1 are applied to the sample 3, and from the sample 3, in addition to the fluorescent X-ray C-Kα ray 4 to be analyzed from carbon in the sample 3, Fluorescence X from iron
The line Fe-Lα line 4 is also generated. Here, conventionally, these fluorescent X-rays are directly incident on the spectroscopic element, C-Kα rays from carbon in the sample are diffracted, and Fe-Lα rays from iron in the sample are converted into Ni / Excitation of carbon in the spectroscopic element, which is an artificial cumulative film of C, generates fluorescent X-ray C-Kα radiation.
Therefore, in addition to C-Kα rays from carbon in the sample to be analyzed, C-Kα rays from unnecessary carbon in the spectroscopic element are incident on the detector, and the S / N ratio and the accuracy of the calibration curve in the analysis are reduced. Had declined.

In the prior art, since the cause of the decrease in the S / N ratio and the accuracy of the calibration curve was unknown, the C-Kα ray was mainly transmitted between the spectroscopic element and the detector to allow the C-Kα ray to pass through.
Attempts have been made to arrange a polymer filter that absorbs X-rays on the shorter wavelength side than the absorption edge, but in this case, C-Kα rays from carbon in the spectroscopic element to be removed should also be analyzed. The C-Kα rays from the carbon in the sample are transmitted while being slightly absorbed and enter the detector, and the sensitivity of the entire apparatus is simply reduced, and the problem cannot be solved.

On the other hand, in this embodiment, the fluorescent X-ray C-Kα ray 4 to be analyzed from the carbon in the sample 3 and the fluorescent X-ray Fe-Lα ray 4 from the iron in the sample 3 are: The light enters the filter 9 before the light enters the spectral element 5. The polypropylene constituting the filter 9 transmits the C-Kα ray 4 well,
Since it has a property of absorbing the Lα ray 4, the C-Kα ray 4 to be analyzed from the carbon in the sample 3 is hardly reduced in the X-rays incident on the spectroscopic element 5, Fe-Lα rays 4 are reduced. The reason why the filter 9 is made of polypropylene or the like containing only carbon and hydrogen is here. If the filter 9 is made of, for example, polyester containing oxygen and the like, the Fe-Lα ray 4 to be absorbed is changed due to the difference in mass absorption coefficient between oxygen and carbon. Absorption is reduced, and as a result, Fe-L
Excitation of carbon in the spectroscopic element 5 by the α rays 4 is not sufficiently suppressed.

As a result, in the spectroscopic element 5, C-Kα rays to be analyzed from the carbon in the sample 3 are diffracted, and the carbon in the spectroscopic element 5 is excited by the The generation of the line C-Kα line is suppressed, and the X-ray 6 incident on the detector 7 is almost only the C-Kα line 4 to be analyzed from the carbon in the sample 3. Thereby, the accuracy of the SN ratio and the calibration curve in the analysis is improved.

Using a standard sample having a known carbon content, a calibration curve of C-Kα radiation was prepared in a conventional apparatus without a filter and in the apparatus of this embodiment, and the X-ray analysis value and the true value (known value) were obtained. The accuracy is defined as the standard deviation of the difference from the chemical analysis value of
%, The accuracy of the apparatus of this example was 0.013%, and the effect of the present invention was proved.

When analyzing the carbon contained in the sample 3 which is an oxide, that is, when oxygen is contained in the sample 3, the fluorescent X-ray O-
It is necessary to suppress the Kα ray 4 from exciting carbon in the spectroscopic element 5, and further, a second-order higher order ray 4 of the O-Kα ray
Is diffracted by the spectroscopic element 5 and is incident on the detector 7 so that C-Kα
The interference spectrum of the line should also be suppressed.
For this reason, namely, the C-Kα ray 4 generated from the sample 3
In order to sufficiently absorb the O-Kα ray 4 while transmitting as much as possible, the filter 9 is preferably made of polypropylene having a thickness of 2 μm or more and 8 μm or less, more preferably a thickness of 4 μm or more and 6 μm or less. In the present embodiment, the filter 9 is attached to the spectroscopic element 5, but the sample 3
The fluorescent X-rays 4 generated from the light source need only be disposed between the sample 3 and the spectroscopic element 5, and need not be attached to the spectroscopic element 5.

[Brief description of the drawings]

FIG. 1 is a front view showing an X-ray fluorescence analyzer according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... primary X-ray, 3 ... sample, 4 ... secondary X-ray generated from a sample, 5 ... spectroscopic element, 6 ... X-ray diffracted by a spectroscopic element, 7 ... detector, 9 …filter.

──────────────────────────────────────────────────続 き Continuation of front page (58) Surveyed field (Int.Cl. ⁶ , DB name) G01N 23/223 JICST file (JOIS)

Claims (1)

(57) [Claims] An X-ray source for generating primary X-rays, a spectral element arranged in a path of secondary X-rays generated from a sample irradiated with primary X-rays, and diffracted by the spectral element An X-ray fluorescence analyzer for analyzing carbon in a sample, comprising a detector to which X-rays are incident, wherein a carbon is provided between the sample and the spectroscopic element in a path of a secondary X-ray generated from the sample. And a filter that is made of an organic compound containing as a main component, transmits fluorescent X-rays generated from carbon in the sample, and absorbs the secondary X-rays that excite carbon in the spectroscopic element. X-ray fluorescence analyzer.