Coupled Gel Coprecipitation and Hydrothermal Processing to Synthesise Cubic Structured Compounds in the SrTiO3–SrZrO3 System

The sol–gel coprecipitation method is highly efficient for synthesising a wide range of binary perovskite solid solutions (SSs), which have been under exhaustive study due to their semiconductor and catalytic properties. Therefore, we conducted a systematic study to extend the chemical stability of the cubic structure in Zr4+-rich SS in the system SrTiO3–SrZrO3. The proposed new approach involves in situ gel coprecipitation and simultaneous hydrothermal processing, which was conducted at standard conditions (200 °C for 6 h) in a KOH (5 M) solution under stirring at 130 rpm. The formation of the cubic perovskite-structured SS occurred in the compositional range from 10.0 to 100.0 mol% Ti4+. The particle crystallisation was achieved via the dissolution-crystallisation mechanism, which proceeded rapidly, aided by preliminary gel dehydration and vigorous stirring. The prepared particles, either orthorhombic or cubic, have a unique morphology, resembling a pseudocuboidal shape with rounded edges. The particle size decreases as the Ti4+ content in the SSs increases, due to improved gel solubility. The band gap of the cubic intermediate SSs is sharp, ranging from 3.12 to 3.57 eV; thus, these perovskites can be applied in the development of semiconductor devices and in catalysis. These powders can also be employed as cool pigments due to their high NIR solar irradiance of 80.22%.