Effects of Substituting Feldspar by Brazilian Phyllite in Glazed Porcelain Bodies
The objective of this study was to investigate the effect of substituting feldspar by phyllite in glazed porcelain tiles bodies. Therefore, the behaviour during firing of a typical body containing feldspar and of another in which feldspar was substituted by the same weight percentage of phyllite were comparatively evaluated. The results showed that the behaviour during firing was significantly different. Water absorption decrease and linear shrinkage increase with increasing temperature began earlier in the feldspathic body, and the variation rate was higher in comparison with the phyllitic body. The lower viscosity of the
liquid phase present in the feldspathic body in relation to phyllitic, estimated by the Giordano Model, is a possible explanation for the observed differences. Other aspects such as different melting temperature of the fluxing mineral as well as the liquid phase volume may also have influenced the observed behaviour.