Sintering characteristics of porcelain

Sintering experiments in the temperature range 1050° to 1300°C using a eutectic glass (as present in a triaxial porcelain) and several constituents in porcelain compositions indicate that shrinkage behaviour of porcelain is primarily controlled by the reaction between glass (or felspar) and clay components. An equation to predict the relationship between the relative density change and shrinkage has been developed, which is based on the liquid phase formation on particles and migration of liquid from the neck regions to the void space. The predicted relationship $\text{Δ}\text{L}\text{L}{}_0\text{=}\text{4π}\text{9β}$$\text{(}\text{1}\text{ϕ}{}_0\text{−}\text{1}\text{ϕ}\text{)}$ (where β is a geometric constant and calculable) fitted the data well. The mechanism of densification appears to change with temperature - initially controlled by reaction then followed by precipitation. The calculated apparent activation energy during the second stage (∼ 60 Kcal/mole) is about half of that obtained by previous workers.