Sintering is a densification process occurring during a heat treatment in powders systems, which involves a reduction in porosity and volume (shrinkage).
Traditional sintered ceramic bodies, like stone-ware or porcelain-ware, achieve densification through mass transfer by means of a mechanism known as glassy phase viscous flow. In a viscous flow sintering process, the driving force is mainly given by the surface tension of the liquid glassy phase and the speed of the process is controlled by the viscosity of the glassy phase.
Sintering behavior can be successfully studied by means of optical dilatometry. The relationship between sintering speed at constant heating rate versus temperature or shrinkage versus time at constant temperature can be exactly determined.
Only with a non contact dilatometer it becomes possible to follow the sintering behaviour of a ceramic material when the driving force of the sintering process is the surface tension of a liquid phase. The optical dilatometry results can be used to define the best heat treatment for each specific material.