JP3147976B2 - Qualitative analysis of amorphous samples - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a qualitative analysis method for an amorphous portion of a sample, such as a mixture of a crystalline portion and an amorphous portion, using an X-ray diffractometer.

[0002]

2. Description of the Related Art Conventionally, X-ray diffraction has been used for qualitative analysis of crystalline samples. This is because the crystalline sample shows several distinct diffraction lines in the X-ray diffraction image, and since the group of diffraction lines indicates the crystal structure of the sample, the sample substance can be identified from the diffraction lines. Only shows the X-ray intensity scattered pattern distributed gently across the X-ray diffraction pattern is a wide angular range of amorphous contrast, since the special diffraction line does not appear, it has not been utilized for sample identification .

[0003]

SUMMARY OF THE INVENTION The present invention provides a method for qualitatively analyzing an amorphous substance of a sample which is amorphous or a mixture of a crystalline part and an amorphous part using an X-ray diffractometer.

[0004]

Means for Solving the Problems Profile data of X-ray scattering characteristics of various non-crystalline substances by an X-ray diffractometer are stored, and a sample is measured from data of an X-ray scattering pattern of the sample to be measured by the X-ray diffractometer. The scattered X-ray profile excluding the peak of the diffraction line due to the crystal part was obtained, and a substance having the highest degree of coincidence with the previously stored scattering characteristic profiles of various substances was searched for.

[0005]

The X-ray scattering pattern peculiar to each substance is exhibited even in an amorphous sample. Since this scattering pattern has a gentle shape, it can be easily distinguished from the peak of a crystalline diffraction line.
Therefore, even if the sample is a mixture of crystalline and non-crystalline materials, the scattering pattern of only the non-crystalline materials can be measured. As described above, the amorphous scattering pattern has a shape unique to a substance, and the shape is stored in advance. By comparing the scattering pattern of the sample with the shape, the qualitative determination of the amorphous portion of the sample can be performed. . The present invention is not intended to distinguish between a crystalline diffraction image and a non-crystalline scattering image, and the present invention can be applied to the qualitative determination of a non-crystalline sample that does not include a crystalline portion. Needless to say,

[0006]

FIG. 1 is a flowchart showing an outline of an embodiment of the present invention. The angular distribution of the scattered X-ray intensity of an amorphous standard sample is measured in advance by an X-ray diffractometer and stored in a data file of a data processor (A).
Thereafter, the angular distribution of the scattered X-ray intensity is measured for the actual sample, and the obtained data is stored in the memory (b). Thereafter, data processing is performed on the measurement result. The data processing removes the diffraction line peak due to the crystal component in the sample from the data of the measurement result (c), and the profile of the measurement data flattened by removing the diffraction line peak and the scattering X-ray intensity of the data file various standard substances The degree of approximation to the profile of the angle distribution is sequentially calculated (d), and the standard substance having the highest degree of approximation is searched out (e) and displayed. The above explanation is about the analysis of only the non-crystalline component in the sample. However, in the case of the sample in which the crystalline component and the non-crystalline component are mixed, the crystal component is obtained by various methods known by the diffraction X-ray peak. It is needless to say that the identification is also performed.

An example of the above processes (c) and (d) will be described. The measurement data stored in the memory is subjected to a smoothing process to obtain data of a smooth scattered X-ray profile. This data is collected at every step of the angle feed of the X-ray diffractometer from the side where the X-ray scattering angle is small to the side where it is large. As shown in FIG. 2, a difference between adjacent data is determined in order from the side having the smallest scattering angle, and the scattering angle a when this difference exceeds a reference value is determined as the starting point of the diffraction X-ray peak and the side having the larger difference. The scattering angle b when the value falls below the reference value from is set as the end point of the diffraction X-ray peak. The measurement values at the measurement points A and B, which were obtained from the start point and the end point of each diffraction line peak by a predetermined number of points away from the peaks, were connected by straight lines, and the peaks of the diffraction X-rays were excluded. A part of the scattered X-ray intensity profile.

FIG. 3A shows a scattered X-ray profile excluding the diffraction X-ray peak. FIG. 3B is a scattered X-ray profile of one of the standard materials stored in the data file. The sampling points of these data are 1, 2,..., I. An example of the calculation of the degree of approximation of both profiles is performed as follows. It is assumed that the X-ray intensity of the sample to be measured with respect to the sampling points 1, 2,. First, Ki = Iui / Isi is determined, and the average of Ki, K = ΣKi / n, is determined. The degree of coincidence E can be expressed as E = 1− | (ΣIui−KΣIsi) | / ΣIui or logarithm, and logK = Σ (logIui−logIsi) / n E = 1−Σ | (logIui−logKIsi) | / ΣlogIui Good.

Alternatively, the degree of coincidence may be determined using the least squares method as follows. K is determined so that the sum of squares of the difference when the measured data is multiplied by a constant K and subtracted from the data of the standard sample is minimized. That is, K that minimizes the sum of squares S = Σ (Iui−KIsi) ² (1) is obtained. The above equation is differentiated by K and set to 0. That is, −2Σ (Iui−KIsi) Isi = 0 From the above equation, ΣIuiIsi = KΣIsi ^{2, and} thus K = ΣIuiIsi / ΣIsi ² . Is the name of the non-crystalline substance of the sample to be measured. The above sum of squares S can be rearranged by putting equation (2) into equation (1): S = ΣIui ² − (ΣIuiIsi) ² / ΣIsi ² (3) (3) Can be calculated in advance and stored in a data file. Therefore, in the process of data processing, for the second term on the right side of equation (3), Σ
The IuiIsi and ShigumaIsi ² calculated (3) may be obtained an S substituted into equation.

[0010]

According to the present invention, an amorphous sample can be identified using an X-ray diffractometer. Since an X-ray diffractometer can be used to perform a qualitative analysis of a crystalline material, the introduction of the method of the present invention makes it possible to analyze both a crystalline sample, an amorphous sample, and a sample in which both are mixed by the same device.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an embodiment of the method of the present invention.

FIG. 2 is an example of a profile showing an angular distribution of scattered X-ray intensity by an X-ray diffractometer.

FIG. 3 is a profile of scattered X-rays (A) due to an amorphous component of a sample and scattered X-rays of a standard sample.

Claims (1)

(57) [Claims] 1. A profile of X-ray scattering characteristics of various non-crystalline standard samples by an X-ray diffractometer is stored, and a profile of a sample to be measured is scattered by the X-ray diffractometer, and the profile of the X-ray is measured. If the sample contains crystalline material, the diffraction X-ray peaks due to the crystal components in the sample are removed, and the degree of coincidence with the X-ray scattering characteristics profiles of various standard samples stored in advance is obtained, and the sample substance is obtained. A qualitative analysis method for a non-crystalline sample, characterized by identifying the non-crystalline component of (1) as a standard sample substance having the highest degree of coincidence.