Phase separation in sol-gel derived ZrO2-SiO2 nanostructured materials

Textures formed by phase separation and crystallization of sol-gel derived ZrO2-SiO2 materials with 30 mol% ZrO2, were examined by X-ray diffraction, small angle X-ray scattering and transmission electron microscopy. An amorphous phase separation consisting in silica-rich and zirconia-rich interconnected domains was shown to be present before crystallization. In the initial stage crystallization of metastable tetragonal zirconia, nucleation was considered to occur in the ZrO2-rich regions. The size and spatial distribution of crystalline particles, dispersed in the amorphous SiO2-rich matrix, are controlled by the phase separation texture.