Vitrification paths in porcelain Stoneware: Dependence on bulk chemical composition and effect on sintering behaviour

This study investigates the vitrification paths of porcelain stoneware, focusing on how bulk chemical compositions can influence sintering behaviour. In particular, leveraging the largest compositional database ever analysed in this context, the research aims to understand how the chemistry of ceramic bodies can influence phase transformations during the firing and thus the properties of the liquid phase at high temperatures. Porcelain stoneware compositions analysed were classified according to their alumosity – defined as the ratio of alumina to the sum of alumina and total flux oxides – and silica content. Four distinct compositional fields were identified: meta-aluminous, moderately peraluminous, frankly peraluminous, and strongly peraluminous. Each category exhibits specific vitrification paths, i.e., the nature, rate and extent of phase reactions that determine the amount and composition of the liquid phase at high temperature, and sintering behaviours. The study emphasizes the complex relationship between batch composition, phase evolution, and sintering kinetics. It demonstrates how variations in alumosity impact liquid phase development and characteristics, affecting key factors such as viscosity, surface tension, and densification efficiency. This comprehensive analysis offers new insights into porcelain stoneware manufacturing and introduces a predictive approach to batch formulation that complements conventional technological assessments. The findings hold significant potential to improve the design and optimization of porcelain stoneware compositions in industrial applications.