JP2866471B2 - Monochromatic X-ray diffractometer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray diffractometer for identifying a sample and performing other analysis by measuring the intensity of diffracted X-rays diffracted by the sample. In particular, the present invention relates to a so-called monochromatic X-ray diffractometer, in which a curved crystal monochromator is arranged on an X-ray traveling path to monochromaticize X-rays for measurement.

[Prior Art] Generally, X is performed for the purpose of identifying a powder sample or the like.
In X-ray diffraction measurement, monochromatic X-rays,
Lines are used. In normal measurement, Kα ray is selected as the X-ray of the single wavelength.

Conventionally, X-rays emitted from an X-ray source, that is, continuous X-rays including X-rays of various wavelengths have been monochromaticized as X-rays.
There is known a method of installing a Kβ filter on a line traveling path to attenuate absorption of X-rays other than Kα rays such as Kβ rays.

There is also known a method in which a curved crystal monochromator is arranged on an X-ray traveling path, and only Kα rays are diffracted and extracted by the monochromator. Conventionally, as a curved crystal monochromator used in this case, graphite, lithium fluoride (LiF), and the like, in which a mosaic angle in a rocking curve has a large spread, have been generally used.

[Problems to be Solved by the Invention] As described above, it is well known that monochromatic X-rays, that is, Kα rays are used in X-ray diffraction measurement. It is formed by different types of X-rays, namely Kα1 and Kα2 rays. For example, when a copper (Cu) target is used as a target (anti-cathode) of the X-ray source, as shown in FIG. 4, the Kα1 line and the Kα2 line having a wavelength difference Δλ of about 3.8 × 10 ⁻³ Å are Kα. Included in the line.

In a conventional monochromatic X-ray diffractometer using a curved crystal monochromator made of graphite or the like or a Kβ filter, an X-ray diffraction curve is obtained by directly measuring the intensity of Kα rays including both Kα1 and Kα2 rays. And analyzed the sample based on the X-ray diffraction curve. For example, when a certain powder sample is subjected to X-ray diffraction measurement by the above-mentioned conventional method, an X-ray diffraction curve having a shape as shown in FIG. 5 is obtained. Among these curves, the X-ray intensity peak P1 appears with the Kα1 ray, and the other X-ray intensity peak P2 appears with the Kα2 ray.

When X-ray diffraction measurement is performed on another type of powder sample, an X-ray diffraction curve having a shape as shown in FIG. 6 is obtained. In this curve, the X-ray intensity peaks P1, P2, and P3 are caused by the Kα1 ray. In the sample used for this measurement, the lattice spacing da of these three peaks is da.
And db are very small, the intensity peaks P4, P5, P6 due to the Kα2 line are mixed with the intensity peaks P1, P2, P3 due to the Kα1 line. In the illustrated example, the intensity peak due to the Kα2 line
P5 is completely mixed into the intensity peak P3 due to the Kα1 line, and both are indistinguishable.

As described above, in the conventional X-ray diffraction measurement using the Kα doublet including both the Kα1 ray and the Kα2 ray,
X-ray intensity peaks due to the α1 and Kα2 double lines are mixed, and a sharp and accurate X-ray diffraction curve cannot be obtained, so that accurate sample analysis cannot be performed.

The present invention has been made in view of the above-described problems in the conventional apparatus, and has achieved extremely accurate measurement by separating Kα2 rays from X-rays used for measurement and enabling measurement using only Kα1 rays. It is an object of the present invention to provide an X-ray diffraction device capable of obtaining a proper X-ray diffraction curve.

[Means for Solving the Problems] To achieve the above object, the first X-ray diffractometer according to the present invention irradiates a sample with X-rays radiated from an X-ray source and diffracts the sample. An X-ray diffractometer for detecting the intensity of diffracted X-rays by an X-ray detector while scanning and rotating a sample.
This is an X-ray diffraction apparatus provided with a light receiving slit and a curved crystal monochromator on a line traveling path, and is characterized by the following points. That is, the slit width of the light receiving slit is Fw, the distance between the light receiving slit and the curved crystal monochromator is L, and the wavelength is generated based on the wavelength difference (Δλ) between the Kα1 line and the Kα2 line. When the angle variance between the Kα1 line and the Kα2 line in the curved crystal monochromator is Δθ, Fw ≦ L × Δθ is set.

The second X-ray diffractometer irradiates a sample with X-rays emitted from an X-ray source, and measures the intensity of the diffracted X-ray diffracted by the sample while scanning and rotating the sample, using an X-ray detector. An X-ray diffractometer for detecting the X-ray from the X-ray source.
An X-ray diffraction apparatus having a light receiving slit, a curved crystal monochromator, and a concentrated point slit on an X-ray traveling path leading to a ray detector, wherein the slit width of the concentrated point slit is FX, the concentrated point slit and the curved crystal The distance between the monochromator and the monochromator is represented by K, and the angular dispersion between the Kα1 line and the Kα2 line in the curved crystal monochromator generated based on the wavelength difference (Δλ) between the Kα1 line and the Kα2 line is represented by Δθ. Is set so that FX ≦ K × Δθ.

In each of the X-ray diffractometers described above, the curved crystal monochromator is capable of elastic deformation and is a single crystal having a small mosaic angle spread in a rocking curve, for example,
It is preferably SiO ₂ , Ge (germanium), Si (silicon), or the like.

Here, the rocking curve is an X-ray diffraction pattern generally used in the past when evaluating the integrity of a single crystal sample, and can be obtained by, for example, the following measurement method. That is, as shown in FIG. 8, an X-ray radiated from the X-ray source 2 is made incident on the first crystal 3 having almost no defect and having high perfection, thereby obtaining a parallel diffraction beam. The light is incident on the single crystal sample 4. The intensity of the diffracted X-ray diffracted by the single crystal sample 4 is measured by the X-ray detector 5. When the single crystal sample 4 is swung by a small angle ω about the diffraction X-ray intensity peak point, a peak pattern having a certain width W as shown in FIG. 9 is obtained.
Generally, this peak figure is called a rocking curve.

The above peak width W is correlated with the mosaic angle spread of the single crystal sample. As shown by the curve A, the peak width W of a crystal having a large mosaic angle spread, for example, graphite or LiF (hookah lithium), is increased. Become wider. On the other hand, crystals having a small mosaic angle spread, for example, SiO ₂ , Ge
(Germanium), Si (silicon), etc. have a narrow peak width W as shown by a curve B and exhibit a sharp diffraction curve.

In the present invention, it is preferable to configure a curved crystal monochromator using a single crystal having a narrow rocking curve peak width, that is, a small mosaic angle spread.

The angular dispersion (Δθ) between the Kα1 line and the Kα2 line means that the Kα1 line and the Kα2 line simultaneously enter an arbitrary point Q on the curved crystal monochromator 1 as shown in FIG. When both are diffracted there, it refers to the angle range formed by the two incident Kα1 and Kα2 lines. Therefore, if this is expressed numerically in consideration of Bragg's diffraction condition, It is represented by

[Function] In the monochromatic X-ray diffractometer according to claim 1, X-ray source X
X-rays incident on the sample or X-rays diffracted from the sample by the light receiving slit installed on the X-ray traveling path to the X-ray detector
The line width of the line is limited. In this case, the spread of the angle of the X-ray which is limited by the light receiving slit and enters one point of the curved crystal monochromator becomes narrower than the angular dispersion (Δθ) between the Kα1 line and the Kα2 line regarding the curved crystal monochromator. . This prevents the Kα1 line from passing through the light receiving slit and diffracted by the curved crystal monochromator, and at the same time, prevents the Kα2 line from passing through the light receiving slit. (Preventing the other from proceeding) can be reliably performed. As a result, it becomes possible to obtain an X-ray diffraction curve using only the Kα1 ray without mixing of the Kα2 ray.

By the way, the X-ray diffractometer according to the present invention scans and rotates the sample, the light receiving slit and the X-ray detector,
The intensity of the diffracted X-ray from the sample is measured. Moving the light receiving slit by scanning rotation does not completely prevent the progression of the Kα2 line, and at some moment some Kα2 line must arrive at the curved crystal monochromator through the light receiving slit. Means
However, even in such a case, according to the present invention, since the diffraction condition of black in the curved crystal monochromator is set in accordance with the wavelength of the Kα1 line passing through the light receiving slit, there is a provision. Even if the Kα2 ray instantaneously passes through the light receiving slit and reaches the curved crystal monochromator, the black diffraction condition is not satisfied, so that diffraction does not occur there and the further progression of the Kα2 ray is completely prevented. You.

In the X-ray diffractometer according to the second aspect, the traveling of the Kα2 ray is prevented by a combination of a converging point slit and a curved crystal monochromator instead of the light receiving slit.

If a curved crystal monochromator is formed by a single crystal having a small mosaic angle spread as in claim 3,
If the angle of the diffraction condition in the monochromator is set so as to match the Kα1 line, the progress of the Kα2 line can be more reliably prevented.

Embodiment FIG. 1 shows an embodiment of the monochromatic X-ray diffractometer according to the present invention. In the figure, an X-ray radiated from an X-ray source 2 in an X-ray tube 6 is applied to a powder sample 7 to be measured while a divergence angle in a horizontal plane is restricted by a divergence slit 8, and the sample is further irradiated with the X-ray. Diffracted at 7.

The diffracted X-rays diffracted by the sample 7 pass through a scattering slit 9 for preventing the progress of scattered X-rays and the like, and further pass through a light receiving slit 10 arranged mainly for extracting Kα rays, and then bend. The light is irradiated to the crystal monochromator 1 and diffracted again. This diffracted X-ray is received by the X-ray detector 12 via the converging point slit 16 and its X-ray intensity is measured.

The sample 7 is supported by a column-shaped sample stage 13 and rotates at a very small speed around a rotation axis ω (extending in the direction perpendicular to the plane of the paper) (referred to as θ rotation).

The scattering slit 9, the light receiving slit 10, and the curved crystal monochromator 1 are fixedly arranged on a first counter arm 14 that rotates independently of the sample stage 13 about the sample rotation axis ω. . The curved crystal monochromator 1 has a fine rotation mechanism to enable fine angle adjustment.
It is provided on the first counter arm 14 via 15.
The concentrated point slit 16 and the X-ray detector 12 are fixedly arranged on a second counter arm 17 integrated with the first counter arm 14. The first counter arm 14 and the second counter arm 17 perform scanning rotation (referred to as 2θ rotation) in the same direction at twice the rotation speed (θ rotation) of the sample around the sample rotation axis ω.

As described above, the X-ray detector 12 measures the diffracted X-ray intensity from the sample 7 while rotating the sample 7 by θ and rotating the first and second counter arms 14 and 17 by 2θ in synchronization with the rotation. And a target X-ray diffraction curve is obtained.

As described above with reference to FIG. 7, there is an angular dispersion (Δθ) between the Kα1 line and the Kα2 line that enter and diffract at an arbitrary point on the curved crystal monochromator 1. In this embodiment, when the distance between the divergence slit 10 and the curved crystal monochromator 1 is L, the slit width FW of the divergence slit 10 is set such that FW ≦ L × Δθ.

With this setting, the Kα1 line and the Kα2 line that are diffracted and progress on the powder sample 7 are simultaneously divergent.
Therefore, at the time when the Kα1 ray is diffracted by the curved crystal monochromator 1, the Kα2 ray can be blocked and the Kα1 ray alone can be spectrally extracted.

In FIG. 1, as described above, the divergent slit 10 scans and moves about the sample rotation axis ω with the 2θ scanning rotation of the first counter arm 14.
As described above, since the divergence slit 10 moves in the direction crossing the X-ray traveling path, the traveling of the Kα2 ray cannot be completely interrupted, and the slight Kα2 ray Is inevitable to pass through the divergence slit 10 and reach the curved crystal monochromator 1.

However, in this case, the K
The angle of incidence of α2 ray is the so-called Bragg diffraction condition 2d ・ si
nθ = λ (however, d: crystal lattice spacing, θ: X-ray incident angle, λ:
X-ray wavelength), and the Kα2 ray does not diffract. As a result, the progression of the Kα2 line is prevented.

In this case, the single crystal constituting the curved crystal monochromator 1 has a peak width W in the rocking curve (FIG. 9).
It is preferable to use a material having a small width, that is, a material having a small spread of the mosaic angle and capable of elastic deformation. As such a single crystal, SiO ₂ , Ge (germanium), Si (silicon) and the like can be considered. As described above, it is advantageous to use a single crystal having a small spread of the mosaic angle because, when the X-ray diffraction condition for the curved crystal monochromator 1 is adapted to the Kα1 ray, the curved crystal monochromator 1 is used. This is because even if the Kα2 ray is incident, the diffraction condition is not satisfied, and the progress of the Kα2 ray by diffraction can be reliably prevented.

As described above, when the X-ray diffraction measurement is performed using only the Kα1 ray while the progress of the Kα2 ray is stopped, the conventional Kα
In an apparatus using a double line (an X-ray including both Kα1 and Kα2), a sample exhibiting an X-ray diffraction curve as shown in FIG. 5 shows a peak due to only the Kα1 line as shown in FIG.
A result indicating P1 was obtained. In addition, a crystal as shown in FIG. 3 was obtained from a sample exhibiting the results shown in FIG. 6 by the conventional apparatus. In any case, the peak appearing in the X-ray diffraction curve is caused only by the Kα1 line, and the data is not disturbed by the mixture of the Kα2 line. Therefore, extremely accurate sample analysis can be performed.

In the above description, the combination of the light receiving slit 10 and the curved crystal monochromator 1 prevents the Kα2 line from traveling and extracts only the Kα1 line.
However, instead of the light receiving slit 10, a concentrated point slit
Similar monochromaticity can also be achieved using 16. In this case, if the slit width of the converging point slit 16 is FX and the distance between the converging point slit 16 and the curved crystal monochromator 1 is K, then FX ≦ K × Δθ is set. Δθ is the angular dispersion between the Kα1 line and the Kα2 line for the curved crystal monochromator 1 as described above.

As described above, the present invention has been described with reference to the preferred embodiments.
The present invention is not limited to the embodiment.

For example, in the above embodiment, the combination of the light receiving slit 10 and the curved crystal monochromator 1 or the focusing point slit
16 in combination with curved crystal monochromator 1
The two-wire blocking mechanism was disposed on the downstream side of the sample 7 (left side in the figure) with respect to the X-ray traveling path. However, it is also possible to arrange the above Kα2 ray blocking mechanism on the upstream side of the sample 7, that is, between the X-ray source 2 and the sample 7. However,
When such an arrangement mechanism is employed, a troublesome operation of adjusting the optical axis between the Kα1 line after exiting the curved crystal monochromator and the measurement sample 7 must be performed, Furthermore, since the X-ray tube 6 itself is a very large device and a Kα2 ray blocking mechanism including a curved crystal monochromator must be installed near the X-ray tube 6, space is unreasonable. Therefore, the installation position of the Kα2 ray blocking mechanism including the curved crystal monochromator is preferably on the downstream side of the sample 7 as in the embodiment of FIG.

[Effects of the Invention] According to the present invention, the progress of the Kα2 ray included in the Kα doublet is prevented, X-ray diffraction measurement using only Kα1 becomes possible, and extremely accurate sample analysis can be performed. Became.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a monochromatic X-ray diffractometer according to the present invention, and FIGS. 2 and 3 are graphs showing diffraction X-ray curves as measurement results by the monochromatic X-ray diffractometer. 4
The figure is a spectrum diagram of a Kα doublet, FIGS. 5 and 6 are graphs showing the results of X-ray diffraction measurement using a conventional Kα doublet, and FIG. 7 is the angular dispersion between the Kα1 line and the Kα2 line ( Δ
θ), FIG. 8 is a schematic diagram showing an example of a method of measuring a rocking curve, and FIG. 9 is a graph showing a rocking curve for several types of single crystals. 2 ... X-ray source, 7 ... powder sample, 12 ... X-ray detector, 10
...... Reception slit, 1 ... Curved crystal monochromator, 16
… Focus point slit, 13… Sample stage, 14… First counter arm, 17… Second counter arm

Claims (4)

(57) [Claims] An X-ray diffractometer for irradiating a sample with X-rays emitted from an X-ray source and detecting the intensity of diffracted X-rays diffracted by the sample by an X-ray detector while scanning and rotating the sample. In an X-ray diffraction apparatus having a light receiving slit and a curved crystal monochromator on an X-ray traveling path from the X-ray source to the X-ray detector, the slit width of the light receiving slit is set to Fw; The distance between the curved crystal monochromator is L; the angular dispersion between the Kα1 line and the Kα2 line in the curved crystal monochromator, which is generated based on the wavelength difference (Δλ) between the Kα1 line and the Kα2 line. A monochromatic X-ray diffractometer, wherein Fw ≦ L × Δθ, where Δθ; 2. An X-ray diffractometer for irradiating a sample with X-rays emitted from an X-ray source and detecting the intensity of diffracted X-rays diffracted by the sample by an X-ray detector while scanning and rotating the sample. An X-ray diffractometer having a light receiving slit, a curved crystal monochromator, and a convergence point slit on an X-ray traveling path from the X-ray source to the X-ray detector, wherein a slit width of the convergence point slit is FX The distance between the converging point slit and the curved crystal monochromator is K; the Kα1 line and the Kα2 line in the curved crystal monochromator, which are generated based on the wavelength difference (Δλ) between the Kα1 line and the Kα2 line. Where X is the angle variance between Δθ; and FX ≦ K × Δθ. 3. The monochromatic X-ray according to claim 1, wherein the curved crystal monochromator is made of a single crystal capable of elastic deformation and having a small mosaic angle spread in a rocking curve. Diffraction device. 4. The monochromatic X-ray diffractometer according to claim 1, wherein the curved crystal monochromator is arranged on the X-ray traveling path downstream of the sample in the X-ray traveling direction.