Synthesis and characterization of chloroborosilicate glasses in the K2O–BaO–Al2O3–B2O3–SiO2–BaCl2 system

Abstract Generally borosilicate glasses are rarely used in photonic applications. Here we modified borosilicate glass by incorporating BaCl 2 with a view to their application in the area of photonics. Chloroborosilicate glasses in the system with general composition (mol%) (100 − x)(42SiO 2 –30B 2 O 3 –20BaO–4K 2 O–4Al 2 O 3 )–xBaCl 2 (where x = 0–30) were prepared by the melt quench technique. All the glasses were found to be X-ray amorphous and transparent. They were characterized by X-ray diffraction, infrared and UV–vis-NIR spectral analyses, differential scanning calorimetry, dilatometry, refractive index, dielectric constant measurements, etc. Their glass transition temperature (T g ), coefficient of thermal expansion (CTE), refractive index and dielectric constant have been found to vary in the ranges 614–641 °C, 73–91 × 10 − 7 K − 1 , 1.58–1.63 and 9.79–11.73 respectively. All the properties are found to be controlled by BaCl 2 content. Their covalent character, metallization criterion and Abbe number were found to decrease with increasing BaCl 2 content whereas the molar volume, average molar refraction and electronic polarizability increase with increasing BaCl 2 content. The devitrified materials have been characterized by XRD which manifests the presence of BaCl 2 nanocrystals of sizes 15–30 nm. Thus these glasses have the potential to develop BaCl 2 nanocrystal containing low phonon energy (~ 350 cm − 1 ) glass-ceramics and are promising for different photonic applications.