Effect of firing conditions, filler grain size and quartz content on bending strength and physical properties of sanitaryware porcelain

The effect of filler grain size, quartz content in the filler and firing conditions (sintering temperature, firing time) on the physical and mechanical properties of a sanitary-ware porcelain has been studied in the narrow range of values used by industrial practice. The investigation has been carried out using the Taguchi method for experimental design. Quartz grain size is the most important factor regarding the physical properties and dominates bending strength in two ways, directly by inducing compressive stresses to the vitreous phase and indirectly through the development of a favorable microstructure. The characteristics of the last are discussed in detail. The optimum grain size of quartz was found to be 5–20 μm. This results in 20–30% increase of bending strength compared to the reference porcelain. The results confirm the “Matrix Reinforcement” theory, however, the positive effect of mullite content on bending strength was not observed.