Hydroxyl extinction coefficient of synthetic amorphous powder SiO ₂

Abstract The development of technology for obtaining high‐purity materials for photonics and microelectronics is very relevant. Fused silica glass is widely used material for the manufacturing of optical fibers and various micromechanical devices for navigation and sensorics. This work is dedicated to the study of structural transformations of amorphous synthetic powder SiO ₂ during heating by using the combined methods of differential scanning calorimetry, thermogravimetric analysis, Brunauer–Emmett–Teller analysis, and Infrared spectroscopy. SiO ₂ was obtained using sol‐gel method by hydrolysis of tetraethoxysilane. Amorphous SiO ₂ powder has transformations associated with the closure of mesopores, sintering of the powder and the formation of a high‐temperature modification of cristobalite that occur at temperatures of 908, 1190, and 1308°C accordingly. The most optimal temperature range 700–1000°C for calculating the extinction coefficient was determined, at which the change in the mass of SiO ₂ powder is caused only by the dehydroxylation process. The time and temperature were calculated that is required to break all hydrogen bonds in amorphous SiO ₂ powder upon heating. The extinction coefficient of OH‐groups of amorphous SiO ₂ powder was calculated and found to be 0.22 L/mol·cm for the wavenumber of 4550 cm ⁻¹ and 7.91 L/mol·cm for the main absorption band of 3670 cm ⁻¹ .