XRD diffraction analyzerThe X-ray diffractometer is a key device for analyzing the crystal structure of materials. Its core principle is based on the coherent scattering of X-rays and crystal atoms. By measuring the diffraction angle (i.e. the angle between the X-ray incident direction and the diffraction direction), combined with the Bragg equation and diffraction pattern analysis, it can accurately decode the core structural information of materials such as crystal type, interplanar spacing, and lattice constant, providing objective basis for material composition identification and phase analysis.

　　1、 Core principle: The correlation between diffraction angle and crystal structure

The bridging effect of the Bragg equation: When X-rays irradiate a crystal, the periodically arranged atoms in the crystal scatter the X-rays. When the scattered waves from adjacent crystal planes (parallel planes formed by atomic arrangement) satisfy the "coherence enhancement" condition, diffraction signals are generated. This condition is quantitatively described by the Bragg equation: 2d · sin θ=n λ (d is the interplanar spacing, θ is half of the diffraction angle, n is the diffraction order, and λ is the X-ray wavelength). In the equation, the X-ray wavelength λ is known (such as copper target X-ray λ=1.54 Å), and the interplanar spacing d can be calculated by measuring the diffraction angle 2 θ. d is the "characteristic fingerprint" of the crystal structure - the atomic arrangement of different crystals is different, and the corresponding d value and diffraction angle are also completely different.

The structural characterization significance of diffraction angle: diffraction angle directly reflects the size of interplanar spacing: the smaller the d, the larger the sin θ, and the larger the diffraction angle 2 θ (such as higher atomic density crystal planes with smaller d and usually larger diffraction angles); On the contrary, the larger the d, the smaller the diffraction angle. For example, aluminum with a face centered cubic structure has a d value of approximately 2.338 Å on its (111) crystal plane, corresponding to a diffraction angle of 2 θ of approximately 38.4 °; And for iron with a body centered cubic structure, the d value of the (110) crystal plane is about 2.027 Å, corresponding to a diffraction angle of 2 θ of about 44.7 °. The difference in diffraction angle can quickly distinguish the type of crystal structure.

　　2、 Decoding process: from diffraction angle data to structural information

Phase identification: Match "diffraction angle fingerprint": Each crystal phase has a unique "diffraction angle relative intensity" spectrum (i.e. standard PDF card). In XRD testing, the instrument scans different diffraction angles of 2 θ (usually within the range of 5 ° -90 °) and records the intensity of diffraction peaks at corresponding angles; Compare the 2 θ value of the measured diffraction peak with the standard PDF card. If the diffraction angle deviation between the two is ≤ 0.2 ° and the peak intensity ratio is consistent, it can be determined that the material contains the phase. For example, in alloy materials, if the measured spectrum shows diffraction peaks at 2 θ=43.3 °, 50.4 °, and 74.1 °, which match the standard PDF card for copper, it indicates the presence of copper phase in the material.

Lattice constant calculation: Accurate quantification of crystal size: Lattice constant (such as the alpha value of a cubic crystal) is a key parameter that describes the periodicity of crystal atomic arrangement, which can be calculated through diffraction angle and crystal facet index (hkl). Taking a cubic crystal as an example, the relationship between the interplanar spacing d and the lattice constant a is d=a/√ (h ²+k ²+l ²). Combined with the Bragg equation, a=n λ√ (h ²+k ²+l ²)/(2sin θ) can be derived. By measuring the θ value of high angle diffraction peaks (such as 2 θ>60 °, reducing measurement errors) and substituting it into known crystal plane indices (such as (200), (220) crystal planes), the lattice constant a can be calculated to determine whether there is lattice distortion in the crystal (such as diffraction angle shift caused by changes in lattice constant after material stress).

Grain size and stress analysis: subtle changes in diffraction angle: When the material grain size is refined, the diffraction peak widens. By using the Scherrer formula (β=K λ/(Dcos θ), where β is the degree of peak broadening and D is the grain size), combined with the diffraction angle θ and peak width β, the grain size can be calculated; If there is internal stress in the material, the lattice will undergo elastic deformation, resulting in a change in the interplanar spacing d, which in turn causes diffraction angle shift - tensile stress increases d and decreases diffraction angle; The compressive stress reduces d and increases the diffraction angle. The magnitude of internal stress can be quantitatively analyzed by the diffraction angle offset.

3、 Technical advantage: Accurate and efficient structural analysis

XRD diffraction analyzer decodes material structure through diffraction angle without damaging the sample (non-invasive testing), and has high resolution (diffraction angle accuracy can reach ± 0.001 °), which can identify trace phases with a content as low as 1%; The testing process is fast (about 10-30 minutes per scan) and can simultaneously obtain multidimensional structural information such as phase, lattice constant, and grain size. It is widely used in structural analysis of metal materials, ceramics, polymers, minerals, and other fields, providing core data support for material research and quality control.