Tuning of optical parameters of sol-gel synthesized ZrO2 nanoparticles

Present study investigates the influence of annealing temperature on structural and optical properties of ZrO2 nanoparticles. The optical parameters of ZrO2 of different phases have been explored in detail including optical band gap, skin depth, refractive index, and optical conductivity. ZrO2 nanoparticles were synthesized by sol-gel route and annealed at temperatures 500, 600, 700, 800, and, 900 degrees C. The structural and spectroscopic analyses of all samples have been performed by XRD and FTIR techniques. XRD patterns reveal that ZrO2 exists in the tetragonal phase at 500 degrees C temperature, while both monoclinic and tetragonal phases were observed at higher annealing temperatures. The optical band gap of ZrO2 increased from 3.85 to 5.12 eV as the annealing temperature was raised from 500 degrees C to 900 degrees C. Similarly, other optical parameters show variations with respect to annealing temperature. The PL spectra of ZrO2 samples confirm that decreasing oxygen defects with increasing annealing temperature may be responsible for increasing the optical band gap.