Properties and crystallization of Li2O–CaO–Al2O3–SiO2–TiO2glasses

Abstract

The addition of CaO to Li2O–Al2O3–SiO2–TiO2(LAST), forming the Li2O–CaO–Al2O3–SiO2–TiO2(LCAST) system, is used in the preparation of low themal expansion coefficient glass-ceramics. By a progressive weight percent substitution of CaO for SiO2, at constant ratios of concentration of Li2O, Al2O3, and TiO2, a number of properties of these glasses have been studied. The results indicated that these thermal properties increased progressively with increasing CaO concentration. X-ray diffraction analysis was utilized to identify the crystalline phase in glass-ceramics of the Li2O–CaO–Al2O3–SiO2-TiO2system. Thed-spacings of the major crystallites were precisely measured and fitted with those of β-spodumene. The minor crystalline phase of titanite, CaO · TiO2· SiO2, was also present. The average thermal expansion coefficients from 25 to 700 °C were 3.50 × 10−6/°C, 3.81 × 10−6/°C, and 3.91 × 10−6/°C for samples A, B, and C, respectively.