Abstract
The crystallization process and thermal expansion characteristics of glass compositions based on 17.80Li2O–(32.20−x) CaO (xSrO)–50SiO2 system (where x=3, 6, 9 and 12mol%) were investigated. The crystallization characteristics of the glasses, the type of crystalline phases formed as well as the resulting microstructure were traced by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The addition of SrO at the expense of CaO has led to a slight decrease in both the transition (Tg) and softening (Ts) temperatures of the glasses. The main crystalline phases, formed after controlling heat-treatment are lithium metasilicate-Li2SiO3, wollastonite-CaSiO3 together with pseudowollastonite-like phase. The incorporation of Sr into CaSiO3 structure has partially promoted has partially promoted the phase transition from wollastonite to pseudowollastonite-like phase. A slight increase of thermal expansion coefficients (α-values) of the glasses and their corresponding glass–ceramics has been detected. The α-values of the obtained glasses are 114 to 130×10−7°K−1 in the 25–300°C temperature range while those of the crystalline materials are 90 to 121×10−7°K−1 in the 25–700°C temperature range. The present results provide valuable information about the role of Sr2+ in determining the type of crystalline phases formed in the glasses and the thermal expansion data of the material were obtained.
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