The Effect of Quartz and Mullite Phases on Strength of Triaxial Porcelain

Abstract

The Effect of quartz and mullite crystalline phases on the strength of triaxial porcelain in the system quartz-feldspar-kaolin composed of20% wt silica and feldspar/kaolin ratio of 5:8 have been investigated. It was found that secondary mullite crystals enhanced both the compressive strength and elastic properties of porcelain while excess glass formation decreased the fracture strength of porcelain as a result of the combined effect of circumferential cracks around quartz grains and the microcracks within the quartz grains. The former was due to the difference in the thermal expansion coefficient between the glassy and the quartz phases while the latter was due to a- to ~b quartz phase inversions.