Lanthanum doping effects on microstructure and properties of nanostructured ZnO

This work presents a preliminary study of the effects of La dopant concentration on microstructure and properties of nanostructured ZnO fabricated by the electrospinning calcination method. The obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy and their optical properties were analyzed by UV-VIS spectroscopy. Results shows that micron sized ZnO “fluffy” clusters of nanocrystalline rods are obtained, their size and morphology strongly affected by La dopant concentration. Optical bandgap of various La doped ZnO was estimated to have values from 2.6 eV at low dopant concentration up to almost 3 eV for higher concentrations, lower than the bulk ZnO bandgap of 3.37 eV. Theoretical simulations lead to a quite good fit of band-gap variations with the La concentration in the ZnO micropowder but it is suggested that the optical properties are strongly affected by the clusters size and shape. The variation of dielectric constant, with the size of microstructures forming the microclusters, induced by La doping, was also studied with a preliminary computational simulation. The respective results can open new ways for possible predictions for material forms that will be suitable for absorption of specific electromagnetic radiation wavelengths. The advantages of this study stand on its comprehensive, multi-faceted approach to investigate La-doped ZnO, focusing on unique microstructural features, like “fluffy” clusters of crystalline grains and rods. • Extensive experimental investigation of the influence of La concentration (conc.) on the microstructure of nanostructured ZnO. • Theoretical predictions of its impact on the optical propeties (OP) show good fit to observed Eg variations with La conc., suggesting OP intricately linked to clusters size and shape. • The ZnO nanostructures made by the electrospinning calcination method, lead to formation of µm-sized “fluffy” clusters of nanocrystalline rods. • The size, morphology, and overall structure of these clusters were found to be highly sensitive to the conc. of La dopant. • Preliminary computational simulation was done to explore effect of microstructure size/morphology on the dielectric constant.