JPH0827246B2 - Data processing method in X-ray diffraction measurement - Google Patents

Description

TECHNICAL FIELD The present invention relates to a data processing method in the case of measuring the crystallinity of a sample with an X-ray diffractometer, for example.

(Prior art) The degree of crystallinity is high
It is an important parameter related to the property of, and is physically defined by the ratio of the weight of the non-crystalline material contained in the sample to the total weight of the sample including the crystalline material and the amorphous material.

When a sample in which crystalline and amorphous are mixed is measured by X-ray diffraction, a measurement profile in which the crystalline profile displayed as a sharp peak and the amorphous profile drawing a gentle curve overlap each other is found. can get.

The following formula is generally used as a method for calculating the degree of crystallization of a sample from this profile.

Crystallinity = 1 / (1 + L · Ia / Ic) (1) However, Ia: integrated intensity of amorphous data Ic; integrated intensity of crystalline data K; constant Strictly speaking, the degree of crystallinity is in the sample. Is the ratio of the mass of the crystal part to the sum of the mass of the crystal part and the mass of the non-crystal part of
In order to obtain the crystallinity from the X-ray diffraction data, it is necessary to replace the X-ray intensity with mass or the like, so the constant K is introduced in the equation (1). This K is determined by the coefficient for converting the X-ray intensities of the crystalline and the amorphous into the component ratio, and if the coefficient of the crystalline is p and the coefficient of the amorphous is q, then K = q / p. . When the coefficients p and q are different from each other, K becomes a number other than 1, and K is properly obtained experimentally. However, if the application is limited to quality control of a specific product, K =
It may be set to 1, or K may be appropriately set so that the numerical value obtained by the equation (1) becomes a value that can be easily handled as data. For example, in the case of a sample having a high crystallinity in general and a small difference in crystallinity between samples, if K is set to a large value, a small difference in Ia appears as a difference in crystallinity, and the difference in crystallinity between samples is large. It becomes easier to compare.

In order to calculate the above equation, the integrated intensities of the crystalline profile and the amorphous profile data must be determined individually. Conventionally, the parameters of the model function were determined from the data of the measurement profile using the nonlinear least squares method, and the shape of the peak of the crystalline profile was expressed by the model function, and the crystalline profile and the amorphous profile were separated. However, there are various patterns in the actual profile, it is difficult to assume an appropriate model function, and it is difficult to match the actual measurement profile by changing the parameters with a simple model function. There was a problem to say.

(Problems to be Solved by the Invention) An object of the present invention is to more appropriately separate a crystalline profile and an amorphous profile from a measurement profile, and improve the measurement accuracy of crystallinity.

(Means for Solving the Problem) When the X-ray diffraction pattern is a pattern in which a peak diffraction pattern and a halo pattern overlap, X
A standard profile is obtained for peak profile data obtained by performing a smoothing process on the data of the line diffraction pattern and subtracting it from the above X-ray diffraction pattern, and the difference from the standard profile is below a reference value. The X-ray diffraction pattern was separated into a peak pattern and a halo pattern by changing the smoothing strength of the smoothing process and trying the smoothing process.

(Operation) When the sample is irradiated with X-rays and the diffracted X-rays are detected by the sample, when the X-rays with the wavelength λ are diffracted by the crystals in the sample with the lattice spacing d, the Bragg's conditional expression 2d sin θ = nλ A strong detection intensity is obtained at a diffraction angle θ that satisfies Here, the intensity of the diffracted X-ray becomes stronger as the number of crystal grains involved in the diffraction grows appropriately and the number becomes larger, and the peak of the diffracted line becomes sharper. On the other hand, when the crystal becomes finer, the width of the diffraction peak widens,
When it becomes amorphous, the diffraction pattern becomes low and it shows a gentle profile (halo pattern). That is, as the crystallinity in the sample is higher, a sharp detection peak appears in the measurement profile, and the halo pattern becomes weaker. This is utilized to measure the crystallinity of the sample. The present invention is an invention relating to a method for separating the above diffraction peak from a measurement profile in the measurement of the crystallinity.

The present invention properly assumes and separates the amorphous profile that appears as a halo pattern from the measurement profile of X-ray diffraction displayed on the screen, and therefore, at a large number of sampling points selected at appropriate intervals in the diffraction angle direction on the screen. The X-ray intensity is read and smoothing processing is performed. The smoothing process erases short-cycle fluctuations, so that only halo patterns that originally show a gentle and smooth change are extracted and remain. This method can be adapted to any measured profile pattern and can make a better assumption of an amorphous profile without assuming a model pattern.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, 1 is an X-ray diffractometer for irradiating a sample with X-rays and measuring the detection intensity of the diffracted X-rays at a diffraction angle θ, and 2 is data for converting the data obtained by the X-ray diffractometer into digital signals. Interface 3 is a CPU for processing the data obtained from the X-ray diffractometer, 4 is a memory for storing the data, 5 is a display device for displaying the measurement data and the calculation result, 6 is a calculation parameter and calculation is performed from the screen of the display device. It is an input device for inputting measurement data used for.

The processing operation of the measurement data will be described with reference to the flowchart of FIG. Since several diffraction peaks for each sample are separately stored in the memory 4 in a file,
A file containing data of peaks suitable for measuring the crystallinity of the target sample is designated from among them and displayed on the display device 5 (a). Displayed profile (see Figure 3a)
While watching, the sampling interval, the number of points, and the number of calculations for smoothing are determined and set by the input device 6 (a). The amorphous profile is smoothed to obtain the amorphous profile (C). The obtained amorphous profile (Fig. 3b) and the measured profile or the crystalline profile obtained by subtracting the amorphous profile b from the measured profile (Fig. 3c) are displayed together (see Fig. 3). ,
It is visually judged from the screen whether the arithmetic processing performed in (c) is proper (d). In the example of FIG. 3, the peak profile c obtained by subtracting the set amorphous profile from the measurement profile has a tail on the left side, and the top of the set amorphous profile is set too low. That is, it indicates that smoothing is too strong. If it is not proper, the operation returns to the operation (a) and the smoothing calculation is performed again. If it is proper, the crystallinity is calculated according to the above-mentioned formula (1) (e). The calculation result is displayed on the display device 5 (F).

In the above-described embodiment, the operator manually specifies all sampling points used for the analysis of the amorphous profile, but the sampling point intervals (eg, the half-value width of the crystalline peak, etc.), the smoothing unit (eg, 5 points, etc.) and the number of smoothing times (eg, 5 times) may be specified, and the CPU 3 may automatically select sampling points. In addition, the determination method of the step in FIG. 2D is performed, for example, by assuming a Gaussian distribution function from the peak height and half width of the crystalline profile obtained from the calculation, and the deviation amount between this distribution function and the crystalline profile is It is also possible to automatically execute the step (d) by determining that it is appropriate when the value becomes equal to or less than a certain predetermined reference value.

(Effects of the Invention) According to the present invention, it is not necessary to perform a troublesome operation of assuming a model function, and furthermore, an amorphous profile and a crystal are obtained from a measurement profile obtained by X-ray diffraction measurement without compromising subjectivity. Since the quality profile can be separated more properly, the measurement accuracy of the crystallinity is further improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a flow chart of the above embodiment, and FIG. 3 is a profile showing the correlation between the diffraction angle and the detected intensity. 1 ... X-ray diffractometer, 2 ... Interface, 3 ...
CPU, 4 ... Memory, 5 ... Display device, 6 ... Input device.

Claims (1)

[Claims] 1. When the X-ray diffraction pattern is a pattern in which a peak-shaped diffraction pattern and a halo pattern are overlapped with each other, smoothing processing is performed on the data of the X-ray diffraction pattern and subtraction is performed from the X-ray diffraction pattern. When separating the peak pattern and the halo pattern by performing the above, a standard profile shape is obtained from the profile data of the peak pattern obtained by the above subtraction, and the difference between the standard profile shape and the profile data is the reference value. A data processing method in X-ray diffraction measurement, wherein the X-ray diffraction pattern is separated into a peak pattern and a halo pattern by performing the smoothing process with varying the smoothing strength until the following.