Temperature annealing and aluminum atomic concentration effect on structural, morphological and optical properties of ZnO-Al 2 O 3 nanocomposites powders and photocatalytic performances

Abstract

Pure ZnO nanoparticles and ZnO- Al2O3 nanocomposites prepared with Al2O3 content of 10, 20 and 30 atomic ratios were synthetized via Sol-gel method and then calcined for 2 h at different temperature 450 °C, 700 °C and 900 °C. The structural, morphological and optical properties of the powder as-synthetized are investigated. The methylene blue degradation reaction was used to assess the photocatalytic activities of ZnO powders. In the present work, the high purity of the nanoparticles was confirmed by EDS spectra. The XRD results show that ZnO powder has a wurtzite structure. The aluminum in composite powders leads to the appearance of the ZnAl2O4 spinel phase and increasing of annealing temperature reduce the crystallite size. The flower-like morphology was well defined in these nanocomposites with an average size in the nanometer range. Photoluminescence reveals the incorporation of aluminum into the as-synthetized nanocomposites. The optical absorption spectra have been presented the relationship between the band gap, particle size, annealing temperature, Al concentration and Urbach energy. Our result suggests that the annealing temperature 700 ⁰C can be considered as an order-disorder transition temperature. The best characteristics were present in the ZnO-30% at Al nanocomposite which give the best photoactivities.