Evolution of macropores in a glass-ceramic under microwave and conventional sintering

Densification and microstructural evolution of a CaO-ZrO2-SiO2 glass powder were studied during heating in order to produce a glass-ceramic material. Microwave (2.45 GHz) and conventional heating were used for different soaking times and temperatures. Macropores, as visible from the last stage of glass sintering, were monitored as a function of temperature by SEM microscopy and image elaboration. The porosity as a results of micropores has proved to be negligible. Other important densification parameters, such as initial powder size distribution and green pellet density, which would have affected macropores evolution were kept constant. Microwave prepared samples have been compared to conventionally treated ones. The effect of microwaves was to speed up the sintering process, but did not affect the crystallization evolution of glass-ceramic materials differently when compared to the conventional sintering.