SURFACE AND INTERFACE CHARACTERISTICS OF GLAZED WALL TILES IN RELATION TO PINHOLES IN MONOPOROASA TILES

For monoporosa rapid fired tiles, eight fritted glaze formulae were designed to have soda feldspar in place of potash. Various ratios of frit/Kaolin and ZnO/ZrSiO4 were also tried. The properties of surface and interface of glazes were characterized through measuring their diffuse reflectance and pore development by scanning electron microscopy. Results were interpreted in terms of crystallite size and strain calculated from Xray line broadening. The cation coordination assessed by infrared analysis along with composition enlightened the glaze network structure. Detailed structural analyses aimed for future environmental studies. It was found that the reduced bubble formation in frits and hence elimination of pinholes and surface toughness in the glaze were related to high acidic glaze. The variation of ZnO and/or ZrSiO4 affected reflection and chromaticity as well as the size and shape of the pores developed in the interface. Results of stresses produced in the opacifier grains related to thermal expansion data of the glaze.