Synthesis of dopant-free tetragonal zirconia nano-powders with aqueous precursor and their optical properties

A series of novel dopant-free tetragonal zirconia nano-powders have been synthesized simply by the desiccation of inorganic aqueous precursor followed by annealing from 330 to 900 °C. Both phase and microstructure analyses provided a solid proof of pure tetragonal phase formation at annealing temperature as low as 430 °C. Due to ultra-small size (∼5 nm) and high surface energy of the zirconia nano-powders derived from aqueous precursor, the tetragonal structure could be maintained as the dominant phase even after annealing at temperature up to 900 °C. The UV–vis absorption spectrum of the zirconia powders calcined at 430 °C showed a strong absorption band around 218 nm and the direct band gap of 5.48 eV, which was attributed to their good crystallization and ultra-small particle size.