Doping and calcination effect on nanostructured aluminosilicates processed by sol-gel route

Local order changes determined in an aluminosilicate matrix by calcination and addition of iron, yttrium or dysprosium oxides were investigated by X-ray diffraction and infrared spectroscopy. The nanocrystalline phase is reached only by Fe doping and not by the other two dopings. After calcination at temperatures as high as 1200 degrees C, nanocrystalline cristobalite alone is formed in the aluminosilicate matrix, while the doped samples favor the additional growth of mullite and quartz nanocrystals. The aluminosilicate spinel phase was not detected in any of these samples. An additional crystalline phase was only observed in the samples doped with yttrium and dysprosium. The structural units evidenced by FTIR analysis are associated with the crystalline phases identified by X-ray diffraction.