Structural Changes in Bentonite Investigated with In-situ XRD

In many applications, the properties of the swelling clay bentonite are modified by annealing. In-situ X-ray diffraction (XRD) reveals the underlying changes of the atomic structure. Phase transformations are observed at several different temperatures when heating up to 1000 °C.


Bentonite is a swelling clay which can absorb large amounts of water. It is formed from aged volcanic ash and has various applications such as:

  • Drilling mud
  • Binder in molding sands for steel casting
  • Binder in ceramics (pottery)
  • Fining agent in winemaking
  • Substance to clean / detoxify fish tanks
  • Adsorbent for wastewater purification
  • Catalyst for several chemical reactions
  • Filler in cosmetics and pharmaceuticals
  • Absorbing substance in cat litter
  • Barrier material for nuclear waste

Some of these applications imply heating of the bentonite up to high temperatures, which results in tremendous changes in many macroscopic properties (including visual appearance). XRD provides insights into the changes in the atomic structure which lead to the altered material properties. In this application report, XRD measurements are performed in-situ using the Automated Multipurpose Powder X-Ray Diffractometer XRDynamic 500 and the High-Temperature Oven Chamber HTK 1200N, both from Anton Paar.

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