Raman spectroscopy and structural analysis of cubic CsBSi2O6 and orthorhombic Cs2B2Si3O10 crystalline phases obtained by crystallization of Na₂O-Cs₂O-B₂O₃-SiO₂ melts

The crystallization of glasses used for immobilization of radioactive waste is generally undesirable due to potential disruption of the matrix structure with subsequent migration of radionuclides into the environment. However, glass crystallization, being a natural consequence of the establishment of equilibrium in the system, can be employed in the controlled synthesis of glass ceramics having predictable properties and structures. The paper discusses the results of crystallization in the glass-forming system Na2O-Cs2O-B2O3-SiO2 leading to the formation of ordered phases. During crystallization from borosilicate melt, cubic cesium borosilicate CsBSi2O6, as described in the space group I-43d, and orthorhombic Cs2B2Si3O10 (Cmce), were found with different Na2O/Cs2O ratios. A variety of techniques were employed to characterize the generated crystals. Single crystal x-ray diffraction (SXRD) was applied to identify the crystal structure. The crystalline arrangement of the crystals was confirmed using powder x-ray diffraction (PXRD) analysis. The Raman spectra and images of these crystalline phases are reported here for the first time.