Mineralogical Services

Mineralogical Services Home | X-ray Powder Diffraction and Associated Techniques | Products and Services | Contact Information

X-ray Powder Diffraction and Associated Techniques

What is X-ray Diffraction? 

X-ray Diffraction (XRD) is generally the fastest and most reliable method used in the identification and quantification of crystalline materials. The technique utilises the diffraction (reflection) of X-rays from the unique arrangement of atoms in a crystal structure. The technique is particularly useful for materials with grain sizes too small for microscopic identification (ie. clay minerals, soils minerals, dusts etc.). 

What can be analysed by XRD? 

XRD can be used to identify mineral specimens (ie. individual grains, mineral assemblages, weathering products, clay minerals etc.) and industrial products (ie. chemical products, boiler scales, corrosion products, asbestos minerals, furnace slags and ashes, etc.). In fact, just about any type of solid material will produce a diffraction pattern. 

How much sample is required? 

Typically, for qualitative analysis, amounts of approximately 1g are sufficient. In some instances, such as well crystalline materials, single grains (~1mg) can be analysed using special low background silicon sample holders. Whole soil analysis, where the clay fraction is to be extracted, requires 10-50g of the whole sample (depending on the clay percentage). Clay analysis for supplied <2µm fraction requires approximately 200mg. 

Instrumentation 

The laboratory is equipped with two diffractometers, a Philips PW1710 microprocessor controlled PW1050 instrument, and a Philips PW1800 microprocessor controlled instrument. The PW1710 instrument features a 35 position sample changer, fixed divergence slit geometry, and graphite diffracted beam monochromator. The PW1800 instrument features a 121 position sample changer, automatic (variable) divergence slit geometry, and graphite diffracted beam monochromator. X-ray diffraction data can be collected with either cobalt or copper radiation. 

The laboratory also has a high temperature diffractometer attachment, and a range of photographic equipment including Debye-Scherrer, Gandolfi, Guinier, Weissenberg, and precession cameras for single crystal analysis. 

Instrument control is provided by state of the art (in-house) computer software that has been specifically designed with clay mineral analysis in mind. Manipulation and identification of the unknown diffraction pattern is also performed by in-house computer search match software (Xplot). The measured data is compared to a powder diffraction database (ICDD – International Centre for Diffraction Data CD-ROM) of approximately 66,000 standard patterns.