X-ray diffraction or XRD is a popular and widely used method for determining the characterization of materials.
Why is this important? Well, characterization of materials is necessary where the desired outcome is to identify the elements present, as well as the overall structure (i.e. its atomic arrangement) so that an accurate definition of the material can be arrived at.
It sounds complex, so let’s break things down a little more. We are all familiar with how X-rays work, right? Well, this same process is essentially used to examine the makeup of materials.
X-rays are directed at the material and when they collide with its atoms, the path of the X-ray is altered and a reading can be taken that gives insights into the structural properties, phases, and orientation of the material.
The material properties of the sample under investigation and the angle at which the X-rays are applied and detected enable those that are carrying out the test to determine whether they are constructive or destructive.
Bragg’s Law states that X-rays can have constructive or destructive interference with each other.
As such, if the waves are out of phase with each other then this is considered a destructive interference. The easiest way to visualize a destructive interference is by imagining two waves parallel to each other with their peaks coinciding with each other, which results in the X-ray waves canceling each other out.
Conversely, a constructive interference results in alternating peaks and troughs that are in synchronicity with each other. The result visible in such instances is the amplification of the X-ray. The resultant waves from a test enable identification.
So, why is it used? Well, one of the terms that those who engage with XRD testing can expect to encounter many times is, ‘polymorph’. A polymorph is a material that has the same composition but a different structure – that is, it can take many different forms. Take for example carbon, a material that we all know can form into graphite as well as into diamonds.
As such, given that we know there are polymorphs, it is necessary to determine the specific elements and structure of each material investigated so that those concerned know exactly what they are looking at and can, therefore, accurately categorize.
X-ray diffraction allows for quick identification of the phase and unit cell of crystalline materials.
The diffraction pattern that results from this technique is commonly regarded as its DNA and provides the tester with the information that they require to check against the database resources available and accurately identify it.
The applications for X-ray diffraction are many. When presented with unknown materials, this process can help technicians determine its composition, breaking down the combined elements into percentages.
It is also used as a forensic tool, where investigation of materials to match against another sample is necessary. What’s more, it is increasingly used across a diverse range of industries for reverse engineering purposes. This is a process where a finished product or material is investigated to determine its composition so that others can replicate it.
We have only touched on the very basics of XRD but we expect that it is already evident that this is an incredibly valuable tool with applications across a multitude of industries.