Powder X-Ray Diffraction for Analysis of Crystalline Materials

Introduction  

Powder X-ray diffraction (PXRD)  is one of the standard methods for characterizing nanoscale materials. A practical, non-destructive analytical method for examining the phase composition, crystal structure, and orientation of powder, liquid, and solid samples is  X-ray diffraction (XRD).   This Non-Destructive method is primarily used for phase identification of a crystalline material and delivers information on unit cell dimension. The original material is finely ground and homogenized, and the average bulk composition is determined. Powder XRD analysis of a sample provides several pieces of information necessary, complementary to various microscopic and spectroscopic methods, including phase identification, sample purity, crystallite structure size, and, in many instances, morphology. Although widely available and necessary, researchers only sometimes exploit this information in nanoscale materials data and sometimes misinterpret it.

Scope 

Powder X-ray diffraction can usefully determine the structure, phase, content, size, shape, crystallinity, and other significant characteristics of nanoscale materials; however, unambiguous sample characterization nearly always necessitates complementing experimental and computational techniques. Since it’s a bulk method, the data it yields can be compared to data from microscopy to see if microscopic observations on a tiny sample of particles accurately reflect the majority of the sample. Powder XRD data for nanoscale materials can often be straightforward to analyze for the vital information needed, but at other times, it can be pretty complex.

PXRD has a broad scope, encompassing various fields such as

• Materials Science: To analyze metals, ceramics, polymers, and composites to determine phase purity and crystallinity.
• Geology: For mineral identification and quantification in rock and soil samples.
• Chemistry: To characterize new compounds and monitor solid-state reactions.
• Nanotechnology: To study the crystallinity and size of nanoparticles.

How does powder X-ray diffraction work​?

Crystal structure determines the pattern in which diffraction of X-rays occurs. Instead of obtaining the diffraction pattern from a single crystal structure, the X-ray powder diffraction method​ uses a powdered version of the material. This is often much easier and more convenient than single-crystal diffraction because growing single crystals is not required. XRD on powder also provides a diffraction pattern for the bulk material of a crystalline structure solid and not for just a single crystal, which may or may not be representative of the whole material.

Read more: X-ray Powder Diffraction (XRD)

Test Procedure

The general procedure for PXRD involves the following steps:

• Sample Preparation

The powdered sample is loaded onto a sample holder, usually made of non-crystalline material, to avoid background noise.

• Loading the Sample

This improves spatial resolution by concentrating high- and low-energy electrons at a low electrical potential (about 0.02 to 5 kV).  

• Data Collection

The sample is placed in the X-ray diffractometer and exposed to X-rays, which are then detected at different angles by the diffracted rays.

• Data Acquisition

A diffraction pattern is created by measuring the intensity of the diffracted X-rays as a function of the angle. The last stage is the sample and data analysis stage. 

Sample Size and Result Analysis of P-XRD

The following are the sample size and data Interpretation of Powder X-ray diffraction:

Pros and Cons of Powder X-ray Diffraction

The following are the limitations and strengths of Powder X-ray diffraction:

Applications of Powder X-ray diffraction (PXRD)

PXRD has numerous applications across different fields, such as Material Characterization, which involves Determining phase purity, identifying unknown phases, and studying phase transitions in various materials.

• In Nanomaterials, Investigation of the size, shape, and crystallinity of nanoparticles and thin films are derived.

• In Geology, Mineral identification and quantification in complex geological samples are done.

• Similarly, in Forensic Science, the Identification and analysis of substances in criminal investigations are determined.

• P-XRD helps determine polymorphism identification.

Conclusion

X-ray powder diffraction ​is a multi-capable and powerful analytical technique for characterizing crystalline materials. Due to its excellent information on material structure, composition, and properties, this technique has become indispensable in many scientific and industrial areas. As technology advances, PXRD continues to evolve, offering even greater precision in the complex world of crystalline materials.

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