JPH05133910A - X-ray diffraction measure - Google Patents

Abstract

PURPOSE:To eliminate need of individually inputting various measurement conditions for each crystal lattice surface by utilizing a peak constant table at the time of split measurement. CONSTITUTION:In a peak constant table, a surface index (hk1), a distance (d) between crystal lattice surfaces, a diffraction peak angle 2theta p, a measurement starting angle 2theta 1 at a low angle side of the diffraction peak, a measurement ending angle 2theta h on a high angle side, X-ray intensity Ip of the diffraction peak, X-ray intensity I1 at the measurement starting angle 2theta 1, X-ray intensity Ih at the measurement ending angle 2theta h, and an index tau with respect to counting time of a detector are set for each of crystal lattice surface of a sample. The peak constant table is obtained in advance by preliminary measurement, and at the time of measurement this, peak constant table is used to automatically perform split measurement. Thus precise measurement of lattice constants and size measurement of crystals is automatically performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray diffraction measuring method for measuring the properties of a sample by measuring the X-ray diffraction pattern of a powder sample using a diffractometer, and more particularly to a precise measurement of lattice constants and The present invention relates to an X-ray diffraction measurement method applied to so-called divided measurement in which only the vicinity of a diffraction peak is precisely measured, such as crystallite size measurement and quantitative analysis measurement.

[0002]

2. Description of the Related Art A precise measurement of a lattice constant will be described as an example. When the chemical formula of a sample is known, the crystal lattice constant of the sample is often already known. What is the lattice constant?
The lengths of the three vectors that make up the unit cell of the crystal,
b, c and the angles α, β, γ between the three vectors. By the way, even if it is a known substance, its lattice constant slightly changes when this substance becomes a solid solution, is thermally expanded, or is distorted under stress.
In such a case, there is an advantage that the lattice constant is precisely measured. There are also cases where it is desired to know the lattice constant of a known substance more precisely than before.

In order to perform such a precise measurement of the lattice constant, it is first necessary to select a plurality of lattice planes and precisely measure the diffraction peak angle of each lattice plane. The spacing of the lattice plane can be calculated from the peak angle. Then, the lattice constant can be calculated from the lattice plane spacing. The simplest crystal lattice is a cubic crystal, but this cubic crystal has a = b = c and α = β =
Since γ = 90 °, it suffices to find the lattice constant a.
On the other hand, in the most complex triclinic crystal lattice, a,
All six of b, c, α, β and γ must be found.

In order to accurately measure the diffraction peak angle of each grating surface, it is necessary to slow down the scanning speed of the goniometer only near the diffraction peak and measure the diffraction peak profile precisely. .. Then, when moving to the measurement of the next diffraction peak, the scanning speed is increased. That is, it is necessary to perform so-called divisional measurement in which only the target diffraction peak is accurately measured.

There are various methods for determining the angle of the diffraction peak based on the diffraction peak profile, such as the peak top method, the half-value width midpoint method, and the center of gravity method. Also in this case, it is necessary to precisely measure the profile near the diffraction peak. For that, the expected diffraction peak
It is necessary to start the precision measurement from the low angle side which is smaller than the peak angle by a predetermined angle and to finish the precision measurement on the high angle side which is larger than the expected diffraction peak angle by the predetermined angle.

Also, in order to obtain a precise diffraction peak profile, it is necessary to make the detected X-ray intensity sufficiently large. For that purpose, it is necessary to increase the counting time of the detector for a peak having a relatively small diffraction intensity.

[0007]

In the precise measurement of the lattice constant, it is necessary to determine the measurement start angle and the measurement end angle for each lattice surface as described above, and the intensity of the diffraction peak. It is necessary to determine the counting time of the detector according to the above. In the past, these operations required the operator to input the respective lattice planes to the X-ray diffractometer.

[0008] Such a situation was the same in the measurement requiring the divided measurement such as the measurement of the crystallite size in addition to the precise measurement of the lattice constant.

An object of the present invention is to provide an X-ray diffraction measuring method which does not require the input of various measuring conditions for each crystal lattice plane.

[0010]

In the present invention, the peak constant table is prepared before the divided measurement. In this peak constant table, various information regarding the diffraction peak of each lattice plane is set. That is, in the peak constant table, the plane index (hkl), the lattice spacing d, and the diffraction peak angle 2θp for each of the plurality of lattice planes of the sample crystal.
And a measurement start angle 2θl on the low angle side of the diffraction peak,
The measurement end angle 2θh on the high angle side of the diffraction peak, the X-ray intensity Ip of the diffraction peak, and the measurement start angle 2θl
X-ray intensity Il at, the X-ray intensity Ih at the measurement end angle 2θh, and an index τ related to the counting time of the detector.
And are set.

Based on this peak constant table, the X-ray diffraction measurement for a predetermined purpose becomes possible by dividing and measuring only the vicinity of the diffraction peak of the lattice plane to be measured.

[0012]

The following is the procedure for dividing measurement using the peak constant table. First, the lattice plane to be measured is selected in advance. Then, of the selected lattice planes, the diffraction plane on which the diffraction peak exists on the lowest angle side is the diffraction peak.
Accurately measure the profile. In order to do so, the diffractometry is performed at the measurement start angle 2θl of the lattice plane.
The fast go-forward scanning of the goniometer of the computer is brought. And
The measurement start angle 2θl to the measurement end angle 2θh are precisely measured at a predetermined slow scanning speed. At this time, the counting time of the detector is set based on the index τ. When the profile measurement of the diffraction peak is completed,
The same operation is performed on the diffraction peak on the next higher angle side. When the measurement is completed for all the selected lattice planes, a predetermined analysis is performed based on the measurement result. For example, in the case of precise measurement of the lattice constant, the precise angle of the diffraction peak is obtained for each lattice plane, the lattice plane spacing is obtained from these numerical values, and the lattice constant is finally determined.

The peak constant table may be prepared as data for a known substance in advance, or the peak constant table may be obtained by preliminary measurement. In the case of this preliminary measurement, it is sufficient to scan the goniometer uniformly at a relatively high scanning speed.

[0014]

EXAMPLES Table 1 is an example of a peak constant table used in the present invention. This peak constant table relates to SiO2, and the wavelength of the characteristic X-ray used as the X-ray source is CuKα. This peak constant table is stored as data in the control computer attached to the X-ray diffractometer, and is displayed on the display in the form shown in Table 1. This piece
In the example of the K constant table, 10 types of lattice plane indices from (100) to (103) are set. And
The lattice plane to be used for actual measurement can be selected from these, and when selecting it, set ○ in the selection field, and when not selecting, set ×.

[0015]

[Table 1]

For each lattice plane, the lattice plane spacing d, information 2θp, 2θl, 2θh (unit: degree) regarding the diffraction angle, and information Ip, Il, Ih regarding the diffraction intensity (t seconds for the X-ray detector) The count number when actually detected),
Information τ and σ regarding the counting time of the detector and information iD regarding the background inclination are set. Hereinafter, these pieces of information will be described.

FIG. 1 shows information 2θp, 2θl, 2θh regarding the diffraction angle and information Ip, Il, Ih regarding the diffraction intensity for one diffraction peak.

The lattice spacing d is the lattice index (hk) of the lattice plane.
If l) is determined, it can be calculated. The unit of the lattice spacing d in Table 1 is angstrom.

When the lattice spacing d is determined, the diffraction peak angle 2θp can be calculated from the Bragg equation.
Measurement start angle 2θl, measurement end angle 2θh, X-ray intensity Ip of the diffraction peak, and X at the measurement start angle 2θl
Line intensity Il and X-ray intensity I at the measurement end angle 2θh
h is the data of the diffraction peak profile measured in the past.
Data, or by preliminary measurement described later.

The X-ray intensity Ip of the diffraction peak is taken into consideration when determining the full scale for measuring the diffraction peak. σ is called relative standard deviation and is calculated by the following equation 1.

[Equation 1] Here, B represents the background of the diffraction peak, and (Ip-B) represents the net diffraction peak intensity. The relative standard deviation σ indicates the statistical fluctuation of the count number by the X-ray detector. When the count number is large, the relative standard deviation is small and the error due to the statistical fluctuation is small, and when the count number is small, the relative standard deviation is large and the error due to the statistical fluctuation is large. In actual measurement, it is preferable to keep the relative standard deviation to about 1%. For that purpose, it is necessary to make adjustments such as shortening the measurement time for peaks with high strength and lengthening the measurement time for peaks with low strength. become.

Τ is the ratio of the counting time T required to set the relative standard deviation σ to 1% and the actual counting time t when the peak constant table is created. Calculated.

[Equation 2] In this peak constant table, τ when the relative standard deviation is unified to 1% is obtained, but τ when unified to a numerical value other than 1% may be used.

ID is an index representing the degree of background inclination, and is calculated by the following equation 3.

[Equation 3] Here, Imin means the smaller of Ih and Il. The physical meaning of this iD is the intensity difference (Ih-
Il) means how many times the statistical variation of background counts. In general, if peaks overlap, the iD value increases, so it is preferable to exclude such peaks from the analysis target. For example, peaks having an iD of 2 or more are excluded from the targets of divided measurement.

As described above, the three indices σ, τ and iD are calculated based on the X-ray intensities Ip, Il and Ih.
This completes the peak constant table.

Next, a preliminary measurement for completing the peak constant table will be described. If a complete peak constant table has not been created for the sample to be measured, it is necessary to perform preliminary measurements using that sample before the main measurement to complete the peak constant table in advance. There is. When performing the preliminary measurement, the operator inputs in advance the plane index of the lattice plane for which the peak constant table is to be created. In the preliminary measurement, the goniometer is scanned from the low angle side to the high angle side at a constant speed to obtain a rough diffraction pattern. Based on this diffraction pattern, necessary information of each diffraction peak can be obtained in the peak constant table. Actually, when preliminary measurement is performed, the computer automatically sets the information of each diffraction peak in the peak constant table.

Next, a specific example of dividing measurement using a peak constant table will be described. It is assumed that the peak constant table is completed as shown in Table 1. First, a peak to be dividedly measured for the precise measurement of the lattice constant is selected. In general, peaks are selected in the order of iD of 2 or less and smaller σ.
In the example of Table 1, nine peaks are selected. First, of the nine selected surface indices, the goniometer moves to the measurement start angle 2θl = 19.920 ° of the first surface index (100). Then, the measurement is started from here at a predetermined slow scanning speed, and the diffraction peak profile is obtained. When measuring with step scan,
The counting time T in the X-ray detector is τ times the counting time t seconds in the preliminary measurement, that is, 9.61 times. As a result, the error due to statistical fluctuation is kept within 1%. Since the peak constant table of Table 1 is obtained at t = 1 second, the counting time in the divided measurement is 9.61 seconds. Measurement end angle 2θh =
When the angle reaches 21.560, the measurement of this diffraction peak is completed. In the case of continuous scanning, the scanning speed will be determined based on the value of τ. The same measurement as above is performed for the remaining eight diffraction peaks, and the division measurement is completed.

Next, the precise angle of the diffraction peak is obtained from the obtained profile of the diffraction peak. For example, the peak position method is used to determine the angle position where the maximum intensity is obtained as the angle of the diffraction peak. Once the angle of each diffraction peak is obtained,
Based on this, the lattice plane spacing of each diffraction peak is obtained.
Finally, the lattice constant is calculated from each lattice spacing, and the final lattice constant is determined by the extrapolation method or the least squares method.

In the above description, the precise measurement of the lattice constant has been described as an example of dividing measurement using the peak constant table, but the present invention is applied to other applications, for example, crystallite size measurement. It can also be applied to quantitative analysis measurement.

[0028]

As described above, according to the present invention, the peak constant table is prepared in advance and the diffraction peak for each grating plane is prepared before performing various applied measurements that require divisional measurement.
Since the peak information is set, the divided measurement can be automatically carried out using this peak constant table.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of information regarding a diffraction peak.

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[Procedure amendment]

[Submission date] November 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

[Title of the Invention] X Senkai Orihaka constant method

Claims (2)

[Claims] 1. An X-ray diffraction measuring method for measuring the X-ray diffraction pattern of a powder sample using a diffractometer to examine the properties of the sample, wherein a surface index is obtained for each of a plurality of lattice planes of a crystal of the sample. (Hkl), the lattice spacing d, and the diffraction peak angle 2θp
And a measurement start angle 2θl on the low angle side of the diffraction peak,
The measurement end angle 2θh on the high angle side of the diffraction peak, the X-ray intensity Ip of the diffraction peak, and the measurement start angle 2θl
X-ray intensity Il at, the X-ray intensity Ih at the measurement end angle 2θh, and an index τ related to the counting time of the detector.
And a step of preparing a peak constant table in which is set, and a step of separately measuring only the vicinity of the diffraction peak of the grating surface to be measured based on the peak constant table. X-ray diffraction measurement method. 2. The X-ray diffraction measurement method according to claim 1, wherein the peak constant table is obtained by performing preliminary measurement.