Structural study and phase transition investigation in a simple synthesis of porous architected-ZnO nanopowder

• ZnO nanopowders with porous architecture were synthesized by a simple method.
• Spherical ZnO nanoparticles confined in submicronic rectangular shape are obtained.
• Crystal structures are determined temperature in-situ XRD up to 450 °C.
• Structural transitions were analyzed.

In this work, zinc oxide powder with a rectangular-shaped porous architecture, made of numerous spherical nanometric particles, was obtained. A simple precipitation/decomposition procedure was used comprising a zinc oxalate intermediate, obtained from zinc sulfate and oxalic acid without any additives. Detailed studies on zinc oxalate dehydration, decomposition and zinc oxide formation, were carried out using in-situ temperature X-ray diffraction and thermogravimetric analysis. During the investigation, the temperature dependence of particle sizes, lattice parameters and crystal structures of ZnC2O4·2H2O, ZnC2O4 and ZnO nanopowders were analyzed from room temperature to 450 °C. Structural transitions were also discussed. The structure and morphology of the as-prepared ZnO nanopowder were investigated by electron microscopy and compared to the crystalline rectangular shape of ZnC2O4·2H2O. The calcination temperature, counter ion and precipitate agent were found to be related to the product's shape and diameter. Spherical ZnO nanoparticles with diameters of less than 20 nm and a maximum specific surface of 53 m2/g were obtained using this method.

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