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.