A new approach to anorthite porcelain bodies using nonplastic raw materials

New anorthite porcelain bodies using only nonplastic raw materials, such as feldspar, quartz, and aluminous cement, without using a binder were fabricated, and their properties were investigated. The green strength was relatively high due to hardening by the hydration reaction of the aluminous cement with the feldspar in a moist atmosphere. The phases found in the green body were feldspar, CaAl2O4, CaAl4O7, α-quartz and a small amount of CaAl2Si2O8·4H2O. The phases in the fired body were α-quartz, anorthite, glass and a small amount of α-Al2O3; cristobalite formed only at a quartz content of 60 wt.%. Higher flexural strength at a composition containing 30 wt.% feldspar is attributed both to fewer crack origins as a result of appropriate vitrification and to greater residual stress caused by the larger difference in the thermal expansion coefficient between the glass matrix and the quartz and anorthite grains.