Effect of Grain Size of Quartz on Mechanical Strength of Porcelain Body

The effect of grain size of quartz on mechanical strength of porcelain body was examined. The bending strength of the fired body increased with an increase in interplanar spacing of quartz in the fired body, which indicates that the quartz is under a tensile stress. Con-sequently, the glassy matrix surrounding the quartz grains is a compressive stress which acts as prestress, improving mechanical properties. The strength of the body depends on the grain size of quartz, and maximum strengths were obtained at 10-20, 5-10 and <5μm, respectively, fired at 1400°, 1350°-1250°C and 1200°C. Smaller and larger quartz grains gave lower strength, probably because of extensive dissolution and crack generation, respectively.