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The growing demand for fluxes, dictated by the shift toward porcelain stoneware, is urging the ceramic tile industry to find a viable alternative to feldspathic materials. Sericite, a microcrystalline form of muscovite, is present in many ceramic raw materials. It melts during firing and can be a suitable substitute for potassic feldspar. The aim of this study is to understand in depth the effects of replacing feldspar with sericite in porcelain stoneware batches with nearly the same chemical composition. Characterization includes phase composition (X-ray powder diffraction, XRPD Rietveld), melt chemical composition (calculated), sintering behavior (optical thermo-dilatometry), and microstructure (scanning electron microscope (SEM). The results indicate a different vitrification path, mostly in the early stage of sintering, related to the different mineralogical composition and particle size distribution of sericite for K-feldspar. Nevertheless, at temperatures higher than 1150°C, the bodies have similar phase composition, microstructure, melt chemical composition, and physical properties. Densification kinetics is faster in the batch with sericite, while the body with feldspar is able to reach a higher bulk density. [ABSTRACT FROM AUTHOR]

The progressive depletion of the main feldspathic flux deposits in the World is forcing the ceramic industry to search for suitable substitutes. The aim of this study is to assess the potential of some feldspar sources in the Egyptian Eastern Desert, particularly syenites from Abu Khruq, in the manufacture of ceramic tiles. Beneficiated samples obtained by laboratory‐scale mineral processing were tested into porcelain stoneware batches (from 10% to 30% wt in replacement of feldspars) and compared with a reference body through a laboratory reproduction of the industrial processing. The technological behavior of unfired tiles does not suffer any significant alteration due to the use of syenites. On the other hand, syenite‐bearing bodies exhibit some changes in the phase composition and the chemistry of the melt, that turns richer in alkali, especially K2O. The consequently increased sintering rate depends mainly on the viscosity of the liquid phase formed during firing. In conclusion, syenites can be used without technological hindrances to manufacture porcelain stoneware tiles. The firing behavior of syenite‐bearing batches can be reasonably adjusted by setting key parameters (eg, the feldspar amount and the Na/K ratio), but the darker color of fired bodies requires to further lower the iron oxide. [ABSTRACT FROM AUTHOR]