Thermally Treated Soil Clays As Ceramic Raw Materials: Characterization By X-ray Diffraction, Photoacoustic Spectroscopy And Electron Spin Resonance

摘要

Soil clay used as ceramic raw material under heat treatment was investigated using X-ray diffraction, X-ray fluorescence, photoacoustic spectroscopy - PAS and electron spin resonance - ESR. The results indicated the presence of at least three different sites for the Fe~(3+) ions, one of them representative of a set of distorted cubic sites. The optical absorption spectra obtained with the photoacoustic technique showed bands associated with d-d transitions of Fe~(3+) ions. Mullite and hematite were detected in the 1100 ℃ heated samples. Crystalline-amorphous-crystalline transformations were detected between 110 ℃ and 1100 ℃. The conclusion drawn from photoacoustic and magnetic resonance measurements agreed very well with that obtained by X-ray diffraction.