The influence of raw materials on the mineralogy and microstructure of fired sanitary-ware vireous body by syncrotron X-ray computed thomography

China whiteware products represent a large part of ceramic materials and cover a wide range of applications like tile, dinnerware and sanitary-ware. They are mainly formed by a vitreous body which comes from heating above 1100 C a mixture of clays, fluxing agents (typically feldspar) and fillers (typically quartz), after previous processing like, for example, aging, drying and body preparation (Carty and Senapati, 1998). Phase composition of vitreous body has been widely studied in past and is characterized by a glassy matrix with some crystalline phases like mullite, which forms upon heating, and residual filler (Martin-Marquez et al., 2009). Additionally, a well developed porosity can be present, with consequent implication on some technological properties of the materials like mechanical strength (Braganca and Bergman, 2003). Four different industrial sanitary-ware compositions were prepared by fixing the "hard" compound (21 % feldspar, 19 % quartz and 6 % China whiteware waste) and by varying the "plastic" compound with four different industrial clay components (one per sample). After casting procedure, half of each sample was saved to investigate the packing of the green body whilst the other half was fired in a muffle furnace at the peak temperature of 1200 C to investigate the porosity of the fired product, for a total of eight samples. All these eight samples, after previous XRPD characterization, have been investigated by Synchrotron Computed Microtomography at the SYRMEP beamline in phase contrast modality. Data reconstruction have been performed and the microstructure have been evaluated by processing slices with a Matlab written code. In particular, it was possible to focus on voids but also on zircon crystals that come from the 6 % of China whiteware waste, due to their "transmitted" signals which differ from the one of the other phases (i.e. quartz, mullite and glass). For each sample, it was possible to characterize the volume of voids and zircon in terms of total volume and size distribution in the 10-1000 ?m range; moreover, Higgins sphericity index and Flynn diagrams have been determined. The results have been also compared with mercury porosimeter measurements.