Controllable synthesis of metastable tetragonal zirconia nanocrystals using citric acid assisted sol-gel method

Metastable tetragonal ZrO2 nanoparticles and nanosheets were synthesized with citric acid assisted sol-gel method. In this approach, zirconium acetylacetonato, Zr(acac)2, citric acid (CA) and ethylene glycol (EG) were used as the source of Zr4+, the chelating, and solvent agent, respectively. The effects of heat treatment on zirconia phase evolution were investigated. We demonstrate that pure tetragonal nanocrystalline zirconia can be obtained with CA: EG mole ratio=5:1 and calcination temperature 490 °C. The microstructure of the products was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Raman scattering. Finally, Photoluminescence (PL) of nanosheets and nanoparticles were also investigated.