Facile synthesis of zirconia nanoparticles using a salt-assisted ultrasonic spray pyrolysis combined with a citrate precursor method

Current synthesis processes for zirconia nanoparticles require expensive precursors or templates, complex steps and long reaction times, and produce highly agglomerated nanoparticles. In this study, we demonstrated a simple and continuous approach for synthesizing zirconia nanoparticles by combining a salt-assisted ultrasonic spray pyrolysis with a citrate precursor method. This process allows tuning of the morphology and size, where hollow sub-micron particles are transformed to minute nanoparticles by controlling (through a chelating reaction) the diffusion rate of zirconium cations in a pyrolysis step. The synthesized nanoparticles (average diameter: ∼10 nm) are characterized by a highly crystalline tetragonal structure, uniform particle-size distribution, and high specific surface area. A detailed mechanism for generating tiny nanoparticles, via this process, is presented and the optical properties of the nanoparticles are evaluated through an ultraviolet–visible (UV–vis) diffuse reflectance spectrum and converted Kubelka-Munk function.