engleski

ZnO-Al2O3-SiO2 glass ceramics: Influence of composition on crystal phases, crystallite size and appearance

The influence of composition of ZnO-Al2O3-SiO2 glass with TiO2 as nucleating agent on crystal phases, crystallite size, and appearance of prepared glass-ceramics has been investigated. Thirteen samples with different ratios of ZnO, Al2O3, and SiO2 were prepared by melting the batches. As-prepared and nucleated bulk glass samples were studied using differential thermal analysis (DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that gahnite (ZnAl2O4) is the main phase crystallizing in the course of thermal treatment, while corundum (Al2O3), willemite (Zn2SiO4), zinc titanate (Zn2Ti3O8), and rutile (TiO2) appear in some of the samples as minor phases. Without nucleation, gahnite crystallite size impairs transparency in all samples. When the samples are nucleated, a part of them were translucent and dichroic, grey in reflected, and amber-colored in transmitting light. Translucent sample was found to be densely populated with uniformly distributed and irregularly shaped nano-sized gahnite crystal grains.

glass-ceramics ; gahnite ; nucleation ; nanocrystals ; dichroism

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