Processing Li2O-Al2O3-SiO2 (LAS) glass-ceramic with and without P2O5 through bulk and sintering route

Commercially significant Li2O-Al2O3-SiO2 (LAS) glass composition with P2O5 content varying between 0 - 6.8 mol% were prepared through the conventional melt-quenching route. From high-temperature dilation results, it was found that different amount of P2O5 in the LAS glass greatly influences the phase transformation (glass transition, softening and melting) characteristics. Two LAS glass systems, namely 3.1 mol% of P2O5 (P3.1) and without P2O5 (P0) were considered further towards making low expansion glass-ceramic using bulk and sin tering route due to their contrary thermal behaviour. The optimum nucleation temperature for P0 and P3.1 glass system was determined to be 640 and 700 degrees C, respectively using the Marotta method. Effect of heat-treatment temperature on the thermal expansion behaviours of the LAS glass-ceramic is explained in detail. Negative thermal expansion (NTE) and low expansion glass-ceramics were produced from bulk and sintering route. Transparent beta-quartz s.s. based ultra-low thermal expansion (0.04 x10(-6) degrees C-1 between -60 degrees C and 400 degrees C) glassceramic was produced.