X-Ray Diffraction analysis (XRD) is a characterization technique used for crystalline materials. In order to measure the intensities and angle of scattering of the X-rays that leave a material, XRD bombards it with incident X-rays. The patterns formed during X-ray diffraction are unique to the periodic atomic arrangements in a specimen and are widely used for phase identification.
X-Ray Diffraction
X-Ray Diffraction analysis (XRD) is a characterization technique used for crystalline materials. X-ray diffraction patterns are unique to the periodic atomic arrangements in a specimen and are widely used for phase identification. In a diffractometer, incident X-rays are scattered (diffracted) at specific angles from the sample’s lattice planes, resulting in diffraction peaks characteristic of simple’s crystal structure. The electron is the scatterer in this event, which is referred to as elastic scattering. The diffraction patterns give information like phase, atomic plane spacing (d-spacing), crystal structure, preferred orientation (texture), average grain size, crystallinity, strain, crystallite size, crystal defects, etc.
A regular array of spherical waves results from a regular array of scatterers. These waves interfere destructively in the vast majority of directions, but according to Bragg’s law, they add constructively in the following few directions:
2dsinθ = nλ
Where,
n is an integer,
θ is the incident angle,
d is the distance between diffracting planes, and
λ is the wavelength of the beam.
Identification of materials based on their diffraction pattern is one of the main applications of XRD analysis. In addition to phase identification, it also reveals information on how internal stresses and flaws cause actual structures to diverge from ideal ones. XRD is used extensively for mineral exploration, identification of new and unknown materials, substrate characterization in integrated circuit production, protein crystallography, solid-state drug analysis, etc. Various XRD configurations are available to suit the type of application.
XRD Variants:
- X-ray powder diffraction (XRPD) Typically used for the analysis of polycrystalline substances. Samples can be powder, solid, pellet, or thin-films.
- X-ray reflectivity (XRR) Good option for multi-layer thin-films characterization for information like layer thickness, density, composition, roughness, etc.
- High-resolution XRD (HRXRD) Mostly used for single crystal (epitaxial) thin films and substrate analysis.
- Grazing incidence XRD (GI-XRD) Suitable for polycrystalline, substrate deposited, or ion-irradiated thin-films, where traditional XRD might penetrate too deep into the substrate.
- Micro XRD Widely used for micron to nm scale crystallographic exploration of samples.
Video 01: What is X-ray diffraction
XRD Common Uses
- Phase identification in bulk, powder, and thin-film samples
- Phase analysis, crystallite size, preferred orientation in polycrystalline compounds.
- Crystalline vs. amorphous percentages in samples
- Crystallography in a wide range of samples, including inorganic and organic materials, polymers, metals, alloys, composites, ceramics, pharmaceuticals, minerals, and nanomaterials
- Detection of faults and defects in crystalline structures, strain distribution in semiconductor materials, residual stress in bulk materials, crystalline impurities in the glass, ceramics, etc.
Advantages
- Non-destructive, high-sensitive, and reliable testing
- Fast run times (~20 minutes)
- Easy sample preparation and operation
- Wide range of acceptable samples (single crystal, bulk/powdered, amorphous materials)
- Databases with standard diffraction patterns available for thousands of materials
- Acceptable thin-films size range: 10um to 2nm
- Easy to interpret qualitative and quantitative data
Limitations
- Hard to characterize mixed, non-homogenous, multi-phase samples, and non-isometric crystals.
- High angle reflections can result in peak overlay.
- No depth profile information
- Minimum spot size of ~ 20µm
Industries
- Microelectronics
- Semiconductors
- Thin-films and coatings
- Glass Manufacturing
- Heavy Metals and Alloys
- Energy storage and Batteries
- Nanomaterials
- Polymers
- Forensic Science
- Geology
- Automotive Materials
- Pharmaceuticals
- Biomedical Research
- Materials Research
XRD Laboratories
- Evans Analytical Group (EAG) Laboratories
- Element Materials Technology
- Intertek Group Plc.
- Attard’s Minerals
- S&N Labs
- EMSL Analytical, Inc.
- Applied Technical Services
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