Some studies on the phase formation and kinetics in TiO2 containing lithium aluminum silicate glasses nucleated by P2O5

Abstract

Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O-71.7SiO2-7.1Al2O3-4.9K2O- 3.2B2O3-1.25P2O5-1.25TiO2 were prepared by the melt quench technique. Crystallization kinetics was investi- gated by the method of Kissinger and Augis-Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interde- pendence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li2SiO3 is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.