Clays and Clay Minerals · 1997 · 51 citations · 30 references
Natural SciencesMaterials SciencePhysicsInorganic ChemistryMagnetic MaterialsSpectroscopyCurie TemperatureFerromagnetismMagnetic SusceptibilityMagnetism Of Inorganic CompoundsMineral ChemistryPhysical Properties Of MineralsKaolinite Group MineralsMagnetic MineralogyMagnetic MineralsMineral Magnetic PropertiesParamagnetic Species
Abstract The Fe 3+ substituted for Al 3+ at the 2 octahedral positions is one of the most common impurities in the kaolinite structure detected by electron paramagnetic resonance (EPR). Evidence has been provided for a relationship between the shape of EPR spectra for structural Fe and the structural disorder in kaolinite. It is proposed that the structural Fe be used as a sensitive probe for the degree of disorder of natural kaolinites. With this aim in view, an EPR disorder index ( E ) is defined from the width of selected EPR lines. Using reference kaolinites, it is shown that this index can account as well for long-range disorder detected by means of X-ray diffraction (XRD) as for local perturbations such as radiation-induced defects (RID). It is shown that the disorder observed through EPR has some points in common with the XRD-measured one. The influence on E of the presence of RID is shown by the study of artificially and naturally irradiated kaolinites.
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