Porcelain tile microstructure: Implications for polished tile properties

The present study was undertaken to determine the influence of sintered porcelain tile microstructure on mechanical properties (fracture strength, modulus of elasticity and fracture toughness) and surface properties (gloss and stain resistance). To obtain sintered specimens with different microstructures the peak firing temperature was varied for bodies made with industrial spray-dried powder, and sets of test compositions were also made in which quartz content and quartz particle size were varied.Liquid-phase sintering is the typical densification mechanism involved in the achievement of minimum porosity, which is characterised by isolated round pores. Bloating occurred above the firing temperature for minimum porosity. Increases in quartz content and quartz particle size in the starting composition led to reduced body sinterability, and thus gave rise to higher porosity in the fired tile.Mechanical properties were adversely affected by an increase in fired tile porosity. For the same variation in porosity, mechanical properties were more sensitive to the change in quartz content than to changes in particle size. No toughening effect was observed with a rise in quartz content or a decrease in particle size: mechanical properties depended primarily on sintered specimen porosity.Gloss and stain resistance (which characterise polished surface quality) varied with surface porosity, both showing the highest values for lowest porosity. The relationship between porosity and gloss was close to linear.