Structural, Crystallographic, and Thermal Properties of Bi12GeO20 for Technological Applications

In this work, we present the structural and thermal properties of the Bi12GeO20 crystal grown using the Czochralski method. X-ray diffraction (XRD) analysis elucidated the crystal structure, while scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) provided information on morphology and elemental composition, respectively. Many peaks belonging to the cubic crystalline structure were observed in the XRD pattern. Thermal behavior was extensively investigated using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). In the crystal, where no serious weight loss was observed up to 863 K, two different weight loss behaviors were observed in the regions between 863 and 1048 K and 1048–1193 K. The behavior observed in these two different regions was associated with two different decomposition and/or evaporation processes, and the activation energies of these processes were determined using the Coats–Redfern equation as 99.7 and 33.1 kJ/mol. As a result of DSC measurements performed with different heating rates, it was observed that an endothermic process occurred around 618 K. The activation energy of this process was found to be 495 kJ/mol using the Kissenger equation. Our findings reveal details about the crystal’s structural arrangement, morphological property, and decomposition/phase transitions, shedding light on the crystal’s potential technological applications in various fields.