Some studies on the phase formation and kinetics in Ti[O.sub.2] containing lithium aluminum silicate glasses nucleated by [P.sub.2][O.sub.5]

Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6[Li.sub.2]O-71.7Si[O.sub.2]-7.1 [Al.sub.2][O.sub.3]-4.9[K.sub.2]O-3.2[B.sub.2][O.sub.3]-1.25 [P.sub.2][O.sub.5]-1.25Ti[O.sub.2] were prepared by the melt quench technique. Crystallization kinetics was investigated 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 interdependence 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 [Li.sub.2]Si[O.sub.3] 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.