Effect of Gd3+ and Al3+ on optical and dielectric properties of ZnO nanoparticle prepared by two-step hydrothermal method

Gd³⁺ and Al³⁺ co-doped ZnO nanoparticles were prepared by hydrothermal method. The effects of dopants on the microstructural, morphological, optical and dielectric properties of host ZnO system were investigated in the present report. The microstructural and morphological investigations of all the samples were carried out by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). To investigate the presence of various intrinsic defects inside the undoped and doped ZnO samples, the Raman spectroscopy and photoluminescence spectroscopy measurements were recorded. The dielectric spectroscopy was carried out as a function of frequency and temperature. The consequences of dielectric measurements suggest that the dielectric response of the 3% Gd³⁺ and Al³⁺ co-doped ZnO sample is significantly enhanced compared to that of undoped ZnO sample. The dielectric response enhances due to the presence of large amount of oxygen vacancies and grain boundaries in the nanostructure of the doped material. All the dielectric parameters confirm the presence of dielectric dispersion inside the doped ZnO samples. The values of dielectric constant as well as ac conductivities were found to decrease at higher concentration of Gd³⁺ and Al³⁺ in the doped ZnO sample and it occurs due to predominating acceptor effect of Al³⁺ at the interstitial site of ZnO nanostructure.