Preparation and characterization of magnesium-aluminium-silicate glass ceramics

Synthesis of machinable quality magnesium aluminium silicate (MgO-Al2O3-SiO 2) for fabrication of insulators/spacers usable in high voltage application s under high vacuum conditions has been carried out following two different routes i,e, (i) sintering route, and (ii) glass route. A three-stage heati ng schedule involving: calcination, nucleation and crystallization, has bee n evolved for the preparation of magnesium aluminium silicate (MAS) glass c eramic with MgF2 as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and machi nability of samples obtained from both routes were investigated. They were also characterized for microhardness. Initial studies on material obtained by glass route reveal that these samples are superior to those obtained fro m sintered route in respect of their high voltage breakdown strength and ou tgassing behaviour. Outgassing rate of 10(-9) Torr l.s(-1) cm(-2) and break down strength of 160 kV/cm were obtained. Different types of spacers, lugs, nuts and bolts have been prepared by direct machining of the indigenously developed glass ceramic.