Enhanced dielectric behavior and ac electrical response in Gd-Mn-ZnO nanoparticles

The investigations of the structural, optical, dielectric and ac electrical properties of Gd0.05MnxZn0.95-xO (weight percentage x = 0.03, 0.05 and 0.07 respectively) nanoparticles have been done in this report. The nanoparticles were synthesized by hydrothermal method. The X-ray diffraction analysis reveals the presence of hexagonal wurtzite crystalline structure for all the undoped and doped samples. Photoluminescence emission spectra for the entire samples confirm the presence of various defect centers inside the doped ZnO wurtzite nanostructure. Dielectric measurements show dispersion behavior for all the samples and it was found to increase with the doping concentration. The dielectric behavior has been explained on the basis of Maxwell-Wagner-Sillars polarization phenomenon. High value of dielectric constant (1.2 × 106) was observed due to the presence of grain boundary defects and oxygen vacancies. Incorporation of Gd and Mn inside the ZnO wurtzite structure can causes more grain boundary defects which can enhance polarization. The ac conductivity of entire samples was temperature and frequency dependent. The ac conductivity was governed by universal ac power law σac = Bωn according to the Jonscher model. Variation of frequency exponent “n” from 0.2841 to 0.0484 suggests that diffusion controlled charge carrier hopping mechanism is also involves in the conduction phenomenon.