Effect of Gd doping on the structural, optical band- gap, dielectric and magnetic properties of ZnO nanoparticles

Nanostructured Zn1-xGdxO delta (0 <= x <= 0.02) powders were synthesized by the combustion reaction method (CR) with the purpose to investigate the effect of Gd doping on the structural, optical band-gap, dielectric and magnetic properties at room temperature. The structure and morphology of all samples were characterized by X-ray diffraction (XRD), and transmission electron microscope (TEM). The XRD patterns of all samples exhibited sharp and intensive peaks of hexagonal wurtzite structure of ZnO without any evidence of spurious crystalline phases. The nanoparticles crystalized in roughly spherical morphology with bimodal particle size distribution centered at similar to 30, similar to 100 and similar to 70, similar to 160 nm for undoped and Gd - doped ZnO (x = 0.02), respectively. Diffuse reflectance spectrum of each sample was obtained by using a UV/VIS/Near spectrometer and the optical band-gap, E-g, values decreased with increasing Gd doping concentration; being similar to 3.23, and similar to 3.17 eV for x = 0 and 0.02, respectively at room temperature. This red shift on the band-gap was discussed in terms of new band levels below the conducting band. Also, the dielectric permittivity data of all samples could be evaluated by the Cole - Cole model. Seems that both oxygen vacancies (V-O) or/and interstitial oxygen (O-i) defects present in the Gd - doped ZnO samples play an important rule in the dielectric permittivity at room temperature. Furthermore, all Gd -doped ZnO samples exhibited typical paramagnetic behavior at rom temperature.