Synthesis of transparent chloroborosilicate nanoglass-ceramics: Crystallization and growth mechanism of BaCl₂ nanocrystals

Abstract

a b s t r a c tOxyfluoride glass-ceramics are extensively being investigated for their excellent optical properties and widespread use in photonic applications. But oxychloride systems are scarcely studied although they are potential candidates for those fields. Here we report chloroborosilicate glass system SiO 2 -B 2 O 3 -BaO-K 2 O-Al 2 O 3 -BaCl 2 (mol%) within which BaCl 2 nanocrystals have been generated by melt-quench technique followed by heat treatment. Samples were characterized by differential scanning calorimetry, X-ray diffraction, infrared and UV-vis spectroscopy, elastic constants measurement, etc. Micro-and nanostructures were analyzed by using FESEM, TEM and SAED. Formation and growth mechanism of BaCl 2 nanocrystals have been demonstrated with the help of schematic representations. Size (7-47 nm) and morphology of the nanocrystals were found to be controlled by temperature and heat-treatment time. Activation energy for crystallization was determined by non-isothermal method using DSC and found to be 510 kJ/mol. Chloroborosilicate glasses containing BaCl 2 nanocrystals having low-phonon energy (∼350 cm −1 ) are promising for different photonic applications.