What Is X-ray Diffraction?

If you’ve ever wondered how scientists can “see” the arrangement of atoms in a material—whether that material is a pharmaceutical drug, a steel alloy, or a handful of clay—X-ray diffraction (XRD) is the technique that makes it possible. It’s one of the quiet workhorses of modern science and industry, hidden inside laboratories and production lines around the world.

XRD tells us how atoms are arranged, what phases are present, and how those structures change with processing, stress, or temperature. Understanding those patterns is key to controlling material properties—from the strength of concrete to the efficiency of catalysts, from the purity of pharmaceuticals and mined goods, to the fertility of soils.

A Basic Overview of X-ray Diffraction

At its core, X-ray diffraction works on a simple principle: X-rays interact with the repeating atomic planes inside a crystal. Because the distance between these planes is on the same order of magnitude as the wavelength of X-rays (a few tenths of a nanometre), the rays are diffracted, forming a diffraction pattern that is unique to the material that produced it. This means:

• X-ray diffraction patterns can act as a fingerprint for materials. You can compare your pattern against a database to see what you have.

• Each component of your material will have it’s own pattern that stack. You can then calculate how much of each component you have (Think quality control, purity assessments in mining, pharmaceuticals and recycling)

• The diffraction pattern can have an atomic model refined against it, letting you fine tune an idea to what you have in reality, be that how much stress your sample contains compared to the original (think wafers, layered materials and rolled metals), how your material expands with absorption (Like batteries absorbing lithium), or how it’s structure changes under novel reactions.

For an experienced eye, those patterns and peaks reveal a wealth of information. Are the phases pure or mixed? Is the material crystalline or amorphous? Are there traces of a contaminant or a high-temperature phase that shouldn’t be there? 

What XRD Can Tell You

1. Phase Identification

Every crystalline material—quartz, steel, calcium carbonate—has a distinct diffraction pattern. Comparing an unknown sample’s pattern to reference databases (such as the ICDD PDF-4) lets us identify which minerals or compounds are present.

2. Quantitative Phase Analysis

Beyond “what’s in it,” XRD can estimate how much of each phase is present. Using full-pattern fitting methods like Rietveld refinement, we can determine relative abundances down to a percent, if an internal standard is included those weight percentages go from relative to absolute, even measuring wt% of amorphous phases. This is vital in mining, cement, and pharmaceuticals where performance depends on phase balance.

3. Crystallite Size and Strain

Peak broadening carries information about the size of crystalline domains and internal microstrain. Nanomaterials, for instance, show wider peaks because their crystals are only tens of nanometres across. 

4. Texture and Preferred Orientation

When crystals align during processing (as in rolled metals or pressed ceramics), their diffraction intensities shift. XRD can quantify that orientation—called texture—which in turn affects mechanical and electrical properties.

5. Lattice Parameters and Residual Stress

By measuring small changes in peak position, XRD reveals variations in lattice spacing caused by composition, temperature, or mechanical stress. This is crucial in alloy design and quality control.

6. Advanced Structure Determination

X-rays inherently interact with the atomic structure, allowing you to model the atomic structure of your molecule, how it packs to form a crystal, or even how your molecule agglomerates and oligomerisation. This is commonly used in pharmaceutical formulation where structural changes make huge differences to the efficacy of the product.

Why XRD Matters Across Industries

Manufacturing and Quality Control

Producers of metals, semiconductors, and ceramics rely on XRD to verify phase composition and detect unwanted polymorphs. A trace of the wrong crystalline form can mean the difference between a robust product and a costly recall.

Pharmaceuticals

Many active pharmaceutical ingredients (APIs) can crystallize in more than one form, known as polymorphs. Each form may dissolve or absorb differently, changing the drug’s effectiveness. XRD is the gold standard for polymorph screening and regulatory compliance. Small Angle Scattering also helps to understand the new Biologic workflow, giving insight into agglomeration and structural changes.

Energy Materials

From lithium-ion batteries to fuel cells and catalysts, XRD helps track how crystal structures change during operation. It identifies the active and inactive phases that determine efficiency and lifetime.

Mining

XRD determines what phases are present, in what quantities, and establishes impurity and tailings content for regulatory purposes.

Geology and Soils

Clays, sands, and silts are mixtures of minerals whose structures govern how water, nutrients, and carbon move through them. XRD identifies those mineral phases precisely—critical for understanding the carbon capacity of your soil, it’s water and nutrient holding capacity and gives you a way to monitor the improvement of your soil in regenerative agriculture.

What XRD Can’t Do (Alone)

While powerful, XRD has its limits. It only sees crystalline material—atoms arranged in regular lattices. Amorphous phases, such as glassy silicates or organic matter, appear only as broad humps.

Also, XRD is bulk-averaged: it tells you what’s in the whole sample, not where each phase is located. For that, one might combine it with scanning electron microscopy (SEM) to image your material to identify it’s components, or X-ray fluorescence (XRF) to give you the exact elemental composition of your sample, this is particularly complimentary to XRD.

Why XRD Remains Essential

Despite being over a century old, X-ray diffraction remains unmatched for non-destructive, precise phase analysis. Its staying power lies in how universally applicable it is: the same physics describes a steel turbine blade, a clay soil, and a pharmaceutical tablet.

Having been the key analytical technique for over 36 Nobel Prizes, XRD is clearly not going away anytime soon. Modern instruments have made XRD faster, cleaner, and more accessible than ever. Compact benchtop diffractometers now sit in small industrial labs, while large synchrotrons handle the cutting edge of research. Yet the underlying principle—Bragg’s simple law of reflection—hasn’t changed since 1913.

At Baskerville X-ray, we see XRD as more than a measurement technique. It’s a window into structure—a way of making invisible order visible. Whether you’re optimizing an industrial process, assessing mineral composition in a field sample, or validating a complex material formulation, XRD offers a direct, quantitative understanding of what’s really there.

The Takeaway

X-ray diffraction might sound esoteric, but it’s one of the most practical analytical tools available. It tells you what your material is made of and how it’s structured, in a way that directly connects to performance, stability, and quality.

In a world that increasingly depends on materials—whether cleaner energy, better soils, or safer drugs—understanding structure means understanding function. XRD provides that bridge.

Next in the Series:

In the next post, we’ll explore in depth how XRD is used in the battery industry to elucidate how structure property relationships determine the batteries capacity, charging rate and even how they are recycled.