Unlocking the Secrets of Materials: The Power of X-ray Diffraction (XRD) and X-ray Fluorescence (XRF)

At RJ Lee Group, the X-ray-based techniques of X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) play pivotal roles in our scientific consulting and materials analysis. These powerful analytical methods provide crucial insights into the composition and structure of materials, making them indispensable tools for our customers across numerous industries.

In this article, we examine how XRD and XRF work, consider their strengths and limitations, and share some examples of the types of applications and industries where they are commonly used.

What is X-ray Diffraction (XRD)?

X-ray Diffraction (XRD) is a non-destructive technique used to identify and quantify the crystalline phases in a material. It works by directing X-rays at a sample and measuring the angles and intensities of the rays scattered by the crystal structures within the sample.

The resulting diffraction pattern provides a fingerprint of the material, revealing its crystalline structure which is compared to over 1 million patterns in the International Centre for Diffraction Data (ICDD) database for phase identification. The XRD diffraction pattern provides other valuable information about the crystal structure including % crystallinity, d-spacing, and crystallite sizing.

Strengths of XRD:

• Highly Accurate Phase Identification: XRD is exceptionally reliable in identifying crystalline phases, making it a go-to for mineral and material analysis.
  
  
• Quantitative Analysis: XRD not only identifies what phases are present in the material but can also provide quantification by Rietveld refinement, providing detailed insight into the material's composition.
  
  
• Quick Analysis: Most qualitative phase identification XRD scans can be analyzed in under 1 hour for quick answers to customers’ urgent problems.
  
  
• Non-Destructive: XRD analysis does not alter or destroy the sample, allowing further testing if needed.
  
  
• Applicable to a Wide Range of Materials: From metals and ceramics to polymers and minerals, XRD can analyze various materials.
  
  

Two of the XRD instruments in use at RJ Lee Group

Limitations of XRD:

• Sample Preparation: XRD requires precise sample preparation to achieve accurate results, and the presence of impurities can complicate analysis.
  
  
• Amorphous Material: XRD/Rietveld refinement provides quantification of amorphous material but cannot provide the composition of non-crystalline materials.

Typical Use Cases for XRD:

• Oil & Gas: Identification of bentonite, an environmental contaminant in drilling fluids.
  
  
• Mineralogy and Geology: Identifying and quantifying minerals in rocks, soils, and sediments.
  
  
• Pharmaceuticals: Analyzing active pharmaceutical ingredients and polymorphs.
  
  
• Material Science: Studying metals, ceramics, and polymers to understand their properties.
  
  
• Batteries: Analysis of electrode materials, including phase identification, crystallite sizing, interplanar spacing, and degree of graphitization.
  
  
• Environmental Science: Assessing contamination and identifying hazardous minerals such as crystalline silica and asbestos.
  
  

What is X-ray Fluorescence (XRF)?

X-ray Fluorescence (XRF) is another non-destructive analytical technique used to determine the elemental composition of a material. By bombarding a sample with X-rays, XRF induces the emission of characteristic "fluorescent" X-rays from the elements within the sample. These emissions are then measured to identify and quantify the elements present.

Strengths of XRF:

• Rapid, Non-Destructive Analysis: XRF can provide quick results without damaging the sample, making it ideal for on-site and in-field analysis.
  
  
• Wide Elemental Range: With the ability to detect elements ranging from fluorine (F) to uranium (U), XRF covers a broad range of the periodic table.
  
  
  
  
• Versatile Sample Preparation: Samples can be prepared as fused beads, pressed pellets, loose powder or polished solid material depending on the sample matrix and customer needs.
  
  
• Quantitative Results: XRF provides both qualitative and quantitative data, delivering detailed insights into the elemental composition of crystalline and amorphous material. A semi-quantitative analysis is available on most sample materials, utilizing the Malvern Panalytical Omnian calibration.
  
  Quantitative analysis is available on common materials such as gypsum, limestone, talc, cement, and fly ash. Loss on ignition (LOI) is included in most XRF analyses as appropriate.
  
  

One of the XRF instruments in use at RJ Lee Group

Limitations of XRF:

• Detection Limits: Low atomic number elements such as lithium, beryllium, boron, carbon, and nitrogen are not included in the XRF analysis.
  
  
• Cannot determine Mineralogy: XRF analysis can determine the chemical composition of a sample, but cannot determine specific mineralogy. Results are presented as elements or common oxides, as appropriate.
  
  
• Sample Matrix Effects: The presence of certain elements can interfere with the detection of others, requiring careful calibration and sometimes additional analytical methods to correct for these effects.

Typical Use Cases for XRF:

• Metals and Alloys: Identifying and quantifying the composition of metals, alloys, and ores.
  
  
• Environmental Testing: Analyzing soil, water, and air particulates for pollutants and hazardous elements.
  
  
• Archaeology and Art Conservation: Determining the composition of artifacts, paintings, and historical materials.
  
  
• Manufacturing Quality Control: Ensuring the consistency and quality of raw materials and finished products in industries like glass, cement, and electronics.

Industries That Rely on XRD and XRF Techniques

• Mining and Mineral Exploration: Both XRD and XRF are critical in identifying and quantifying minerals and ores, guiding exploration and extraction processes.
  
  
• Environmental Science and Geology: Used to assess soil contamination, identify minerals, and monitor environmental pollutants.
  
  
• Pharmaceuticals: XRD is particularly valuable for analyzing the crystalline structure of drug compounds, while XRF helps in identifying trace elements in raw materials.
  
  
• Manufacturing and Quality Control: XRF is widely used in manufacturing for alloy verification, coating thickness measurements, and ensuring material compliance with regulatory standards.
  
  
• Art and Archaeology: Both techniques are used to analyze ancient artifacts, determine the composition of pigments, and authenticate historical pieces without damaging them.

Conclusion

XRD and XRF are both powerful techniques that offer complementary strengths, making them essential tools in the fields of material science, geology, environmental analysis, and beyond. While XRD excels in phase identification and crystalline structure analysis, XRF provides rapid, elemental analysis.

RJ Lee Group scientists understand the unique capabilities and limitations of each method, allowing us to select the most suitable technique for a client’s analytical needs. We utilize greatly enhanced sample preparation techniques to ensure the accuracy and reliability of our results, and our vast range of tools and experience means that unknown coatings, inclusions, and materials are never a problem.