Non-isothermal crystallization kinetics of bismuth germanate glass-ceramics

Glass-ceramics containing bismuth germanate were fabricated using the conventional melt-quenching method. Glasses have been prepared from BiO1.5-GeO2-BO1.5 ternary glass system by focusing on the region of 59 mol% BiO1.5: 23 mol% GeO2: 18 mol% BO1.5. The non-isothermal crystallizations kinetic were studied by thermal analysis at various heating rates of 5, 10, 15, 20 degrees C/min. The resulting glass was analyzed by using differential thermal analysis (DTA) for determining the crystallization temperature (T-p). Then, the prepared glass pieces were heat treated at T-p. The element composition analysis of the quenched glass performed by energy dispersive X-ray fluorescence (EDXRF) analysis. X-ray diffraction (XRD) was used to obtain the phase formation of the heat treated glass-ceramics. Physical properties and their morphologies of the obtained glass-ceramics were also investigated. This crystallization kinetic result can be used to evaluate the crystallization potential of the interesting glasses. In the non-isothermal kinetics process, the average (E-a) value was 302.95 +/- 2.25 kJ/mol. The calculated value of the Avrami parameter (n) by using Ozawa equation was found to be 1.69 which indicated that the crystallization mechanism was diffusion control with a one-dimensional crystal growth.