The role of firing temperature, firing time and quartz grain size on phase-formation, thermal dilatation and water absorption in sanitary-ware vitreous bodies

This work reports a study on (i) the evolution of mineral phases versus time and temperature, and (ii) some relationships between phases observed, process parameters, and macroscopic properties (thermal expansion and water absorption), in sanitary-ware vitreous bodies. These properties are relevant to satisfying the technical requirements of sanitary-ware. We have fixed the green body composition, varying some key process parameters, such as firing temperature (Tf), firing time (tf) and quartz grain size (d50); a grid of 30 Tf-tf-d50 points has been explored. We have spanned the tf-Tf space (0-80min; 1200-1280°C) using firing temperatures representative of the plateau values of the heating curve in industrial processes. X-ray powder diffraction has been used to determine the phase composition for each Tf-tf-d50 point. Scanning electron microscopy proved useful in enhancing the micro-structural characterization. Quartz d50 seems to be the process-parameter which most effectively co-relates with the thermal expansion of the glassy matrix.