JP3708070B2 - X-ray diffraction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray diffraction method using a parallel beam X-ray diffractometer characterized by a sample driving mechanism.
[0002]
[Prior art]
In the technical field of X-ray diffraction, the following are known as well-known techniques closely related to the present invention. The first known technique is sample rocking in the concentration method, which is disclosed in Japanese Patent No. 2904055 (hereinafter referred to as the first document). The second known technique is in-plane rotation of the sample in the parallel beam method, which is disclosed in Japanese Patent Application Laid-Open No. 7-159300 (hereinafter referred to as the second document). A third known technique uses a parabolic multilayer mirror in the incident side optical system of the parallel beam method, and this is disclosed in Japanese Patent Application Laid-Open No. 11-287773 (hereinafter referred to as third document).
[0003]
In the first document, in the concentrated X-ray diffraction optical system, the relative movement of the X-ray source and the X-ray detector (generally θ-2θ scanning) is independent of the sample surface relative to the incident X-ray. The sample is swung around a rotation center line parallel to the sample surface so that the angle formed is changed (this swing is hereinafter referred to as ω swing). This can increase the number of crystal grains that contribute to diffraction when measuring powder samples that are poorly mixed or have large crystal grains, or metals that have become coarse due to heat treatment. it can.
[0004]
[Problems to be solved by the invention]
By the way, if the sample is swung by ω in the concentration method, the surface of the sample deviates from the measurement principle of the concentration method, and the resolution of the measurement result decreases. In addition, it is also known that the sample is rotated in the plane in the concentration method, but in this case, it does not deviate from the measurement principle of the concentration method. It may be insufficient to increase the grain.
[0005]
On the other hand, in the parallel beam method, it is conceivable to move the sample during measurement so that the number of crystal grains contributing to diffraction increases. The above-mentioned second document discloses that the sample is rotated in-plane during measurement in the parallel beam method. If in-plane rotation of the sample is not sufficient, it is possible to oscillate the sample during measurement. In the parallel beam method, since there is no principle restriction like the concentration method, there is no possibility that the resolution of the measurement result is lowered even if the sample is swung ω. However, in the parallel beam method, no specific device is known for realizing both in-plane rotation and ω oscillation of the sample during measurement.
[0006]
By the way, the use of a parabolic multilayer mirror to obtain a parallel beam having a high X-ray intensity is known from the above-mentioned third document. In this third document, a mechanism for in-plane rotation and ω oscillation of the sample is incorporated in the sample stage. However, this in-plane rotation and ω oscillation are not performed during the measurement. This is for setting a suitable sample orientation and orientation.
[0007]
The object of the present invention is to use a parallel beam with a high X-ray intensity, or to devise a sample rocking mechanism that is superior to a simple combination of in-plane rotation and ω rocking, so that even a polycrystalline sample with strong orientation can be used. It is an object of the present invention to provide an X-ray diffraction method capable of performing diffraction measurement while reducing the influence of orientation as much as possible and without reducing the resolution.
[0008]
[Means for Solving the Problems]
The X-ray diffraction method of the present invention includes the following steps. (A) A step of preparing an X-ray diffraction apparatus having the following configurations (a) to (c). (A) an incident-side optical device comprising: an X-ray source; a parabolic multilayer mirror that converts X-rays emitted from the X-ray source into a parallel beam; and a vertical divergence limiting unit that limits the vertical divergence of the parallel beam. system. (B) Optical on the light receiving side provided with a lateral divergence limiting means for limiting the lateral divergence of the diffracted X-rays coming out of the sample and an X-ray detector for detecting the intensity of the diffracted X-rays that have passed through the lateral divergence limiting means system. (C) A sample holding device for holding a sample, an in-plane rotation mechanism that enables in-plane rotation of the sample during measurement, and a ω oscillation mechanism that enables eccentric ω oscillation of the sample surface during measurement A sample holding device. (A) A step of performing X-ray diffraction measurement of a sample by rotating the sample in-plane and performing eccentric ω oscillation of the sample surface during measurement using the X-ray diffractometer.
[0009]
The ω oscillation of the sample is a rotation parallel to the sample surface so that the angle formed by the sample surface with respect to the incident X-ray changes independently of the relative movement between the X-ray source and the X-ray detector in the diffraction measurement. This is a movement that rocks the sample around the center line. The eccentric ω oscillation of the sample surface means ω oscillation such that the sample surface is separated from the rotation center line of the ω oscillation.
[0010]
In the present invention, the X-ray diffractometer further has the following characteristics. (D) The sample holding device includes a support base that can swing around a rotation center line, and a sample base that can move and rotate with respect to the support base. (E) The eccentric ω swing is possible by swinging the support base. (F) The sample stage can move in a direction perpendicular to the rotation center line, and the distance between the sample surface and the rotation center line can be adjusted by this movement. (G) The sample stage can be rotated around the φ axis perpendicular to the rotation center line, and the in-plane rotation is possible by this rotation.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view of one embodiment of an X-ray diffraction apparatus used in the present invention. This X-ray diffractometer employs a parallel beam optical system, and includes an incident side optical system 10, a sample holding device 12, and a light receiving side optical system 14. The incident-side optical system 10 is mounted on a first turntable 16, and the first turntable 16 can rotate around a horizontal rotation center line 18. The optical system 14 on the light receiving side is mounted on the second turntable 20, and the second turntable 20 can rotate around the same rotation center line 18. The sample holding device 12 is fixed to the third turntable 22, and the third turntable 22 can also swing around the same rotation center line 18.
[0012]
The optical system 10 on the incident side includes an X-ray source 24, a parabolic multilayer mirror 26, a solar slit 28 for limiting vertical divergence, and an output width limiting slit 30. Although the X-ray source 24 shows only a linear X-ray focal point in FIG. 1, an X-ray tube including such an X-ray focal point is actually mounted on the first turntable 16. The parabolic multilayer mirror 26 has a reflecting surface that is a parabolic surface, and converts a linear divergent X-ray beam 38 emitted from the X-ray source 24 into a parallel beam 40. An X-ray source 24 is disposed at the focal point of the paraboloid. Such a parabolic multilayer mirror 26 is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-287773, and can produce a parallel beam having a high X-ray intensity. The vertical divergence limiting solar slit 28 is for limiting the divergence (vertical divergence) of X-rays in the direction perpendicular to the diffraction plane (the plane including the incident X-ray beam and the diffracted X-ray beam). The emission width limiting slit 30 is a slit for setting the beam width (beam width in the diffraction plane) and beam position of the parallel beam 40 incident on the sample to a desired width and position.
[0013]
The optical system 14 on the light receiving side includes a solar slit 32 for limiting lateral divergence, a light receiving width limiting slit 34, and an X-ray detector 36 (in this embodiment, a scintillation counter). The lateral divergence limiting solar slit 32 is for limiting the X-ray divergence (lateral divergence) of the diffracted X-rays 42 coming out of the sample within the diffraction plane. In the embodiment, the length of the foil of the solar slit (length in the optical axis direction) is 100 mm (or 200 mm), and the distance between the foils is 100 μm. At this time, the divergence angle of lateral divergence is 0.114 °. (Or 0.057 °).
[0014]
The light receiving width limiting slit 34 is a slit that defines the beam width of the diffracted X-rays incident on the X-ray detector 36 (beam width in the diffraction plane), and has a function of cutting scattered radiation that becomes noise.
[0015]
If the optical system on the incident side and the light receiving side as described above is used, the diffraction measurement with the same high resolution as that of the concentration method can be performed even in the parallel beam method.
[0016]
FIG. 2 is a perspective view of the sample holding device 12. The third turntable 22 can swing around a horizontal rotation center line 18. A support base 44 (in a substantially horizontal state) is fixed perpendicularly to the surface of the third turntable 22. When the third turntable 22 swings around the rotation center line 18, ω swing occurs. A sample table 46 is provided on the support table 44. The sample 50 is set on the surface of the sample table 46. The sample table 46 can move in the vertical direction with respect to the support table 44. By this vertical movement, the distance between the surface of the sample 50 and the rotation center line 18 (distance d in FIG. 3) can be adjusted. Further, the sample stage 46 can rotate around the φ axis 48. The φ axis 48 is perpendicular to the rotation center line 18. The rotation around the φ axis 48 is driven by an electric motor.
[0017]
FIG. 3 is a front view showing the movement of the sample holding device 12. The surface of the sample 50 is separated from the rotation center line 18 by a distance d downward. When the third turntable 22 swings around the rotation center line 18 within a predetermined angle range (that is, when ω swings), the sample 50 also swings. At this time, since the surface of the sample 50 is separated from the rotation center line 18 by the distance d, the X-ray incident angle α with respect to the sample surface changes and the X-ray irradiation region on the sample also shifts. This point will be described later. The maximum possible value of the distance d is determined by the condition that the parallel beam 40 does not deviate from the sample when the sample surface is oscillated eccentrically ω. For example, assuming that the diameter of the sample stage 46 is 25 mm, the line width of the parallel beam 40 at the sample position is 20 mm, and the beam width of the parallel beam 40 is 0.7 mm, the maximum possible value of d is about 0.3 mm. .
[0018]
The sample stage 46 rotates by φ while performing the above-mentioned ω swing. As the ω swings, the φ shaft 48 naturally swings. In the embodiment, the rotation speed of φ rotation is 50-60 rpm, and the cycle of ω swing is about 4 seconds. These rotation and swing speeds can be changed by controlling each electric motor.
[0019]
FIG. 4 is an elevational view of the ω swing mechanism, as viewed from the back side of FIG. In FIG. 1, the third turntable 22 is fixed to a hollow shaft 52, and this hollow shaft 52 is a casing (not shown) that houses a rotation drive mechanism for the first turntable 16 and the second turntable 20. ) Protruding to the back side. As shown in FIG. 4, a ω swing mechanism is attached to the rear end of the hollow shaft 52.
[0020]
In FIG. 4, a swing plate 54 is fixed to the hollow shaft 52. The swing plate 54 can swing around the rotation center line 18 integrally with the hollow shaft 52. An upper end of a tension coil spring 58 is hooked on the pin 56 at the right end of the swing plate 54. The lower end of the tension coil spring 58 is hooked on the pin 60. The pin 60 is fixed to the above casing. Therefore, the swinging plate 54 is always given the rotational moment 62 in the clockwise direction of FIG. On the other hand, a roller 64 is rotatably mounted on a line connecting the rotation center line 18 and the pin 56 on the swing plate 54. The outer peripheral surface of the roller 64 is in contact with the outer peripheral surface of the eccentric cam 66. The outer periphery of the eccentric cam 66 is circular, and the rotation shaft 68 of the eccentric cam 66 is located at a position eccentric to the outer periphery. The rotating shaft 68 is connected to the output shaft of the electric motor.
[0021]
When the eccentric cam 66 rotates around the rotation shaft 68 at a constant speed as indicated by an arrow 70, the roller 64 in contact with the eccentric cam 66 follows the eccentric cam 66 while freely rotating. As a result, the swing plate 54 swings within a predetermined angle range. When the oscillating plate 54 is leveled, the sample surface is leveled. At this time, ω = 0 °. In this embodiment, the swing plate 54 swings within the range of ω = ± 10 °.
[0022]
Next, the effect of ω oscillation on the sample surface will be described. FIG. 5 is an elevation view for explaining an X-ray irradiation region on the sample surface 72 when the sample surface 72 is positioned on the rotation center line 18. When the sample surface 72 is in a horizontal state (ω = 0 °), the incident parallel beam 40 hits the region from the point A to the point B on the sample surface 72. The X-ray irradiation area is indicated by hatching. Since the parallel beam 40 is a linear beam in a direction perpendicular to the paper surface, the points A and B extend in a direction perpendicular to the paper surface.
[0023]
Next, when the sample surface 72 is rotated counterclockwise by 10 ° in FIG. 5, the above points A and B on the sample move to points A1 and B1. At this time, the parallel beam 40 hits an area from point C to point D on the sample. Conversely, when the sample surface 72 is rotated by 10 ° in the clockwise direction in FIG. 5 from the horizontal state, the above points A and B on the sample move to points A2 and B2. At this time, the parallel beam 40 hits the region from point E to point F on the sample.
[0024]
Thus, when the sample is swung by ω, the incident angle of the parallel beam 40 with respect to the sample surface 72 changes variously, and the number of crystal grains contributing to diffraction increases. In addition, the X-ray irradiation area on the sample surface also changes, and the irradiation area contributing to diffraction becomes wider than in the case where ω oscillation is not performed.
[0025]
Next, the eccentric ω oscillation will be described. FIG. 6 is a view similar to FIG. 5 in the case where the sample surface 72 is located at a distance d downward from the rotation center line 18. The parallel beam 40 is at the same position as in FIG. When the sample surface 72 is in a horizontal state (ω = 0 °), the incident parallel beam 40 hits the region from the point A to the point B on the sample surface 72.
[0026]
Next, when the sample surface 72 is swung counterclockwise by 10 ° in FIG. 6, the above points A and B on the sample move to points A1 and B1. At this time, the parallel beam 40 hits the region from point C to point D on the sample. 5 is different from FIG. 5 in that the points C and D are narrowed inward in a substantially symmetrical manner with respect to the points A1 and B1, whereas in FIG. 6, the middle point between the points C and D is different. Is shifted to the right from the midpoint between points A1 and B1.
[0027]
Conversely, when the sample surface 72 is swung by 10 ° clockwise from the horizontal state in FIG. 6, the above points A and B on the sample move to points A2 and B2. At this time, the parallel beam 40 hits the region from point E to point F on the sample. In this case as well, the midpoint between points E and F is greatly shifted to the right than the midpoint between points A2 and B2.
[0028]
As described above, when the sample surface 72 is away from the rotation center line 18, when the sample is swung by ω, the irradiation area on the sample surface 72 is shifted along with the ω swing. For example, in FIG. 5, the distance from point B2 to point F is L1, while in FIG. 6, the distance from point B2 to point F is L2. L2 is larger than L1. Therefore, when the sample surface 72 is oscillated eccentrically ω, the X-ray irradiation area on the sample surface becomes wider than in the case of normal ω oscillation. Eventually, the eccentric ω oscillation of the sample surface has the same effect as moving the sample in translation within the sample surface (moving the X-ray irradiation region). In the present invention, biaxial rotational motion is used. As a result, the effect of combining the biaxial rotational motion and the translational motion is produced.
[0029]
Next, a method for using the X-ray diffraction apparatus of FIG. 1 will be described. The angle of the optical system 14 on the light receiving side (corresponding to the diffraction angle 2θ) is changed relative to the optical system 10 on the incident side, the X-ray intensity is measured by the X-ray detector 36, and the diffraction pattern is recorded. can do. Since this X-ray diffractometer employs a parallel beam method, there is no particular restriction on the angle formed between the optical system on the incident side and the light receiving side and the sample surface. Therefore, in order to change the diffraction angle 2θ described above, (1) the incident side optical system 10 is stationary and the light receiving side optical system 14 is rotated by 2θ, and (2) the incident side optical system 10 is rotated by 2θ. Any scanning method can be employed, such as stopping the optical system 14 on the light receiving side, and (3) rotating the optical system 10 on the incident side and the optical system 14 on the light receiving side symmetrically in the opposite directions by θ. In the measurement results described below, symmetrical θ rotation scanning is executed.
[0030]
In addition to the 2θ scan as described above, the present invention rotates the sample in-plane (φ rotation) and performs eccentric ω rotation of the sample surface during measurement. As a result, even for a sample with strong orientation, the number of crystal grains contributing to diffraction can be increased, and a measurement result close to an ideal powder diffraction pattern can be obtained.
[0031]
In fact, when measuring a highly oriented polycrystalline sample (for example, Portland cement, which is a sample with strong cleaving and difficult to grind), a conventional X-ray diffractometer (sample by the concentration method) is used. Compared with the sample rotated in-plane or sample rotated in-plane by the parallel beam method), a diffraction pattern with less influence of orientation was obtained. And even if the sample was refilled and measured again, the diffraction pattern did not change much compared with the measurement result with the conventional X-ray diffractometer, and it was confirmed that the reproducibility was excellent.
[0032]
The present invention is not limited to the above-described embodiments, and can be modified as follows.
[0033]
(1) In the above embodiment, as shown in FIG. 3, the surface of the sample 50 swings eccentrically ω with the surface away from the rotation center line 18, but on the contrary, the sample 50 The effect is the same even if the eccentric ω swings so that the surface of 50 is away from the rotation center line 18 upward.
[0034]
(2) In the above embodiment, a long solar slit is used as the lateral divergence limiting means on the light receiving side, but instead, an analyzer crystal (a planar artificial multilayer film made of germanium or silicon) or a free space is used. It is also possible to use an object surface multilayer mirror (used in the direction opposite to the incident side, ie, a collimated beam diffracted from the sample is incident to obtain a focused X-ray beam).
[0035]
【The invention's effect】
In the X-ray diffraction method of the present invention, in the parallel beam method, the in-plane rotation of the sample and the eccentric ω oscillation of the sample surface are combined during measurement. The reproducibility is good and high-resolution diffraction measurement is possible.
[Brief description of the drawings]
FIG. 1 is a perspective view of one embodiment of the present invention.
FIG. 2 is a perspective view of a sample holding device.
FIG. 3 is a front view showing the movement of the sample holding device.
FIG. 4 is an elevational view of a ω swing mechanism.
FIG. 5 is an elevational view for explaining an X-ray irradiation region on the sample surface when the sample surface is located on the rotation center line.
FIG. 6 is an explanatory view similar to FIG. 5 in the case where the sample surface is located away from the rotation center line.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Incident side optical system 12 Sample holding device 14 Light receiving side optical system 16 1st turntable 18 Rotation center line 20 2nd turntable 22 3rd turntable 24 X-ray source 26 Parabolic multilayer mirror 28 Vertical divergence limitation Solar slit 30 for light emission Outgoing width limiting slit 32 Horizontal divergence limiting solar slit 34 Light receiving width limiting slit 36 X-ray detector 44 Support base 46 Sample base 48 φ axis

Claims (2)

An X-ray diffraction method comprising the following steps.
(A) A step of preparing an X-ray diffraction apparatus having the following configurations (a) to (c).
(A) an incident-side optical device comprising: an X-ray source; a parabolic multilayer mirror that converts X-rays emitted from the X-ray source into a parallel beam; and a vertical divergence limiting unit that limits the vertical divergence of the parallel beam. system.
(B) Optical on the light receiving side provided with a lateral divergence limiting means for limiting the lateral divergence of the diffracted X-rays coming out of the sample and an X-ray detector for detecting the intensity of the diffracted X-rays that have passed through the lateral divergence limiting means system.
(C) A sample holding device for holding a sample, an in-plane rotation mechanism that enables in-plane rotation of the sample during measurement, and a ω oscillation mechanism that enables eccentric ω oscillation of the sample surface during measurement A sample holding device.
(A) A step of performing X-ray diffraction measurement of a sample by rotating the sample in-plane and performing eccentric ω oscillation of the sample surface during measurement using the X-ray diffractometer. The X-ray diffraction method according to claim 1, wherein the X-ray diffraction apparatus has the following characteristics.
(D) The sample holding device includes a support base that can swing around a rotation center line, and a sample base that can move and rotate with respect to the support base.
(E) The eccentric ω swing is possible by swinging the support base.
(F) The sample stage can move in a direction perpendicular to the rotation center line, and the distance between the sample surface and the rotation center line can be adjusted by this movement.
(G) The sample stage can be rotated around the φ axis perpendicular to the rotation center line, and the in-plane rotation is possible by this rotation.

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