The use of nepheline-syenite in a body mix for porcelain stoneware tiles

In the study, the possibility to use nepheline-syenite, as fluxing agent, in a body mix used for porcelain stoneware tile, was determined. Starting from the reference mix composition, different amounts, 5.0, 10.0 and 15.6 wt.%, of sodium feldspar were replaced with the same amounts of nepheline-syenite. Different sintering cycles were used to understand the role of the nepheline-syenite in the development of the final microstructure. The presence of nepheline-syenite strongly favours the sintering behaviour, by reducing the sintering time necessary to reach the water absorption values, requested by the International Standard. Furthermore, the microstructure results more homogeneous and the mechanical characteristics are increased. The better mechanical performances can also be attributed to the different mineralogical compositions, in particular with lower amount of glassy phase, higher flexural strength values are obtained.