Effect of the Nature and Concentration of the Fuel on the Structure and Morphology of ZnO Microspheres Produced via Spray Solution Combustion Synthesis

Synthesis of ultradisperse spherical ZnO powders was accomplished by spray solution combustion, employing four distinct fuels, namely methenamine, glycine, urea, and citric acid. Using X-ray diffraction analysis, scanning electron microscopy, and low-temperature nitrogen adsorption, the impact of the main process parameters (composition and concentration of fuel, temperature and rate of the carrier gas flow) on the structure and morphology of ZnO particles was demonstrated. A synthesis temperature of 700°C was found to be sufficient to generate crystalline ZnO with a homogeneous phase composition, regardless of the type and amount of fuel. It was shown that the initial pH of the precursor solution does not affect the formation of the ZnO phase. At rates of carrier gas flow above 4 L min–1, the presence of by-products is detected. It has been determined that the excess and type of fuel significantly affect the morphology of the synthesized ZnO microspheres and can be used to control the technological characteristics of the powder and the kinetics of sintering.