Effect of structural evolutions on optical and electronic properties of co-precipitated ZrO2 nanoparticles

Zirconium dioxide (ZrO₂) nanoparticles are prepared by co-precipitation method using zirconium oxychloride as the precursor, EDTA as the capping agent, sodium hydroxide and deionized water as the solvent. The synthesized NPs were annealed at different temperatures ranging from 673 to 1273 K. Structural evolutions as a function of annealing temperature are analyzed using XRD, Raman and FTIR analysis. Samples annealed up to 673 K are found to be amorphous. Further annealing resulted in the formation of crystalline structure with tetragonal phase. It turned to polycrystalline comprising both tetragonal and monoclinic phase after annealing above 1073 K. Annealing at further higher temperature resulted in crystallization in monoclinic phase. Morphological studies are conducted using FESEM analysis. The particle size distribution is found to be strongly influenced by annealing temperature. A uniform morphology with adequate distribution of nanosized particles of size 10–20 nm is achieved for particles of polycrystalline phase. Optical absorption and bandgap modification studies were conducted using UV–Visible spectroscopy. Modifications in electronic excitation levels and formation of defects as a function of annealing temperature, in the nanoparticles synthesized, were investigated using photoluminescent studies. The effect of structural and morphological evolutions, with annealing temperature, on optical and electronic properties of ZrO₂ nanoparticles are studied in detail.