The Effect of Different Fluxes on Thermal Behavior of Floor Tile Glazes

Nepheline-syenite is a fluxing agent used in sanitary ware, electrical porcelain and chinaware bodies, in order to reduce firing temperature and to increase the alkali level in the liquid glassy phase. Compared to pure feldspars, the advantages coming from the use of nepheline-syenite are: (i) the content of potassium and sodium is higher and (ii) the melting temperature is generally lower than that of potassium-feldspar, which always contains other phases, such as quartz, which shift the melting point to higher temperatures. The content of Al2O3 is high and the content of SiO2 is lower in nepheline-syenite with respect to feldspars (considering that in feldspar Al2O3/SiO2 is about 0.2, whereas in nepheline Al2O3/SiO2 is 0.5). The aim of this study is to compare the influence of the nepheline-syenite and feldspars on the thermal behavior of the floor tile glazes. For this aim; several formulations were prepared with industrial raw materials. After applying the glazes on bodies; the compositions were fired in industrial floor tile kiln ( ≈ 1190 ◦C, for 43 min). Thermal behaviors of glazes were measured by hot stage microscope and the crystalline phases were identified by X-ray diffraction. Color properties and glossiness were measured for comparing the aesthetic characteristics