Pyroxene-based glass-ceramics as glazes for floor tiles

Crystallization of a glass with composition in the diopside primary crystallization field in the MgO–CaO–Al2O3–SiO2 quaternary system was investigated. Also the action of some additives, nucleants and fluxes, in the pyroxene development was examined. Glasses were prepared by conventional melting of a mixture of raw materials and cooled by pouring in water. Pellets of glass powder specimens were thermally treated at several temperatures up to 1200 °C. The crystallization path was followed by X-ray diffraction powder (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The results proved that, in addition to the effect of B2O3 and TiO2 in the development of the final pyroxene phase, some amount of alkaline oxides, Na2O and/or K2O, are required to obtain well-defined morphologies of pyroxene crystals. Fast fired under industrial conditions glass-ceramic glazes on to porcelain stoneware supports improved hardness of final products