Densification and properties of CMAS glass-ceramic prepared from compacts of pressed powders and of tape cast powder multilayers

Calcia magnesia alumina silica (CMAS) glass ceramics containing anorthite, diopside, and barium feldspars as crystalline phases have been fabricated by uniaxial pressing of tape cast glass powder multilayers. The sinterability of the parent glass was investigated from observations of the densification process and the extent of crystallisation determined by changes in the microstructure and mechanical properties of sintered compacts which were prepared below 1100 degrees C. The results showed that glass ceramics produced by tape casting had a higher density and lower porosity than those obtained by uniaxial pressing of loose powders. The tape cast material also showed superior mechanical properties, characterised by Vickers microhardness and elastic modulus, and achieved a higher degree of crystallinity at a temperature 100 K lower than for the pressed powder samples. The low porosity (0.5-1.0%), Vickers hardness (700 HV (25 g)), and elastic modulus (125 GN m(-2)) indicate that the sintering of multilayer tape cast glass powder is a viable method for producing glass ceramics.