Dilatometric study of shrinkage during sintering process for porcelain stoneware body in presence of nepheline syenite

The shrinkage of porcelain stoneware body containing different values of nepheline syenite was investigated. Dilatomeric tests were carried out on suitable specimens to obtain the expansion-shrinkage behavior of ceramic bodies. The differences found in shrinkage data were evaluated by kinetic model and determination of activation energy. The results showed that the activation energy increases with Na2O+K2O/quartz ratio and reaches to constant value when 10.0 wt.% nepheline syenite is added to starting composition. The maximum value of shrinkage also approximately remains constant with increasing fluxing agent. It was found that the fluxing effect of nepheline syenite was quite evident with the observed enhanced rate of densification accompanied by the typical compensation effect.