Crystallization behavior of Li2O-Al2O3-6SiO2glasses containing Ta2O5

Abstract

TiO2and ZrO2have been successful nucleating agents in lithium aluminosilicate glass-ceramics, which have applications including cooking ware, heat exchangers, telescope mirrors, and the matrices of fiber reinforced composites. The major crystalline phases, stuffedβquartz ss (solid solution) andβspodumene ss, have very small volume coefficients of thermal expansion, and thus these glass-ceramics have excellent thermal shock resistance. Ta2O5has recently been established as an effective (phase separation inducing) nucleation catalyst in glasses of this system. The effect of varying (re-heating) thermal treatment on microstructure formation in these glasses with Ta2O5additives is discussed herein.Glass samples were prepared in 100 gram batches using SiO2, Li2CO3, Al2O3, and Ta2O5powders as raw materials. The mixture, 1:1:6 in molar ratio of Li2O:Al2O3:SiO2with 4 mol% Ta2O5, was calcined in a Pt - 3.5% Rh crucible at 1350°C for 2 hours, held for another 12 hours at 1650°C, and then quenched onto a copper plate. The glass and devitrified samples were then mechanically thinned and ion-milled using a liquid nitrogen cold stage.