Properties of Barium Silicate Obtained by Microwave–Hydrothermal (M-H) Method

A microwave–hydrothermal (M-H) method was developed for synthesizing barium silicate from solutions of barium salts and sodium silicate. Advanced techniques (DTA, XRD, IR spectroscopy, SEM and TEM) were used to study the optical, granulometric, electrical and other functional characteristics of barium silicate. BaSiO3 synthesized at 100 °C is an amorphous nano-sized powder (10–20 nm); however, the product synthesized at 240 °C has a crystalline structure (20–27 nm), whereas the crystalline phase of BaSiO3 is typically obtained using known methods at temperatures above 400 °C (12–40 nm). During M-H synthesis, it was found that the structure formation mechanism and particle size of BaSiO3 changed due to the peculiar features of microwave heating. The synthesized barium metasilicate exhibits a high diffuse reflectance coefficient of 92%. It is a wide-band-gap semiconductor with a band gap width of Eg = 4.1 eV. Both amorphous and crystalline phases of BaSiO3 exhibit high photocatalytic activity in the UV range. This study shows that the developed M-H method enables the production of nano-sized powder and enhances the functional properties of barium silicate. Compared with conventional methods, the M-H method is more efficient due to reduced synthesis time and lower energy costs.