Influence of annealing temperature on the structural and optical properties of nanocrystalline zirconium oxide

Abstract Nanocrystalline zirconium oxide powder was prepared by sol-gel method using zirconyl chloride octahydrate (ZrOCl 2 ·8H 2 O) and ethylenediaminetetraacitic acid (EDTA) in ammonium hydroxide (NH 4 OH) solution. The as-synthesized complex product was annealed at 650 °C, 750 °C and 850 °C for 2 h to get fine ZrO 2 powder. These samples were further analyzed by Scanning electron microscopy (SEM), X- ray diffraction (XRD), Energy-dispersive X- ray spectroscopy (EDX), UV-vis analysis, Fourier transform infrared (FT-IR) spectroscopy, Photoluminescence spectroscopy (PL) and Raman Spectroscopy to study their structural and optical properties. The structural studies revealed that nanocrystalline ZrO 2 powder exhibits monoclinic phase with variation in crystallite size with annealing temperature. The UV–vis absorption band edge of ZrO 2 decreases from 514 nm to 451 nm as annealing temperature rises from 650 °C to 750 °C. It seems that the drastic reduction in band gap energy may be one of the novel unexpected characteristics of ZrO 2 . The FTIR analyses further confirmed the formation of nanocrystalline monoclinic ZrO 2 . PL analysis revealed the novel emission peaks at 305 and 565 nm. The Raman spectroscopy confirmed the transformation of amorphous zirconium hydroxide to m -ZrO 2 with increase in temperature from 650 °C to 850 °C.