Some studies on the phase formation and kinetics in TiO2 containing lithium aluminum silicate glasses nucleated by P2O5
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 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 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.
KeywordsAmorphous materials Thermal analysis Electron microscopy X-ray diffraction Thermal expansion
The authors wish to thank Dr. J. V. Yakhmi and Mr. V. K. Handu for their support and encouragement. Thanks are also due to Dr. Shovit Bhattacharya and Mr. Thinaharan for SEM measurements and Dr. A. K. Tyagi for providing XRD facility. They would like to acknowledge the help received from M/s Arjun Sarkar and Rakesh Kumar during glass preparation. Support received from the IFCPAR vide project number 4008-1 is gratefully acknowledged. One of the authors (AA) would like to thank the DAE for awarding him a fellowship.
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