Investigations of the non-isothermal crystallization of Bi4Ge3O12 (2:3) glasses

Amorphous Bi4Ge3O12 glass samples were produced by melt quenching procedure stating with Bi4Ge3O12 (BGO) powder, obtained by solid state reaction between oxides. The kinetics of non-isothermal crystallization of BGO nano-crystals has been investigated. Differential Thermal Analysis (DTA) can give the main parameters of crystallization with an exothermic peak from 813 K to 851 K depending on the heating rate, which was assigned to the crystallization of cubic BGO in the amorphous matrix and compared with the X-Ray Diffraction (XRD) patterns. The nano-crystal dimensions were calculated from the XRD patterns by using the Debye–Scherrer method and were compared with Transmission Electron Microscopy (TEM) images. It was shown that the Ozawa model is most suitable for describing the behavior of non-isothermal crystallization of BGO nano-crystals within the glass matrix. Experimental results suggest a disk-shape type growth mechanism for the Bi4Ge3O12 nano-crystallites. The Flynn–Wall–Ozawa method has shown that the average activated energy value is 385 ± 14 kJ/mol which was computed within the same model and agrees very well with the activation energy of the crystallization.

► Kinetics of non-isothermal crystallization of Bi4Ge3O12 (2:3) glasses. ► Nucleation rates are described by the disk-shape mechanism. ► Differential Thermal Analysis (DTA) compared with the TEM and XRD measurements. ► Ozawa model describes the non-isothermal crystallization of BGO nano-crystals. ► Flynn–Wall–Ozawa method gives the average activated energy value of 385 ± 14 kJ/mol.