Sol-gel auto combustion synthesis, electrical and dielectric properties of Zn1−xCoxO (0.0 ≤ x ≤ 0.36) semiconductor nanoparticles

In the present work, Co2+ ion doped zinc oxide nanoparticles Zn1−xCoxO (x = 0.00, 0.06, 0.12, 0.18, 0.24, 0.30 and 0.36 mol) were synthesized by sol-gel auto combustion method. The effects of heavily doped Co2+ ion concentration on the structural, electrical and dielectric properties were studied. The prepared nanoparticles were characterized by X-ray diffraction technique (XRD), transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and Fourier transform infrared spectroscopy (FT-IR). The X-ray diffraction analysis revealed the formation of single phase having hexagonal wurtzite structure along with secondary phase (Co3O4). TEM analysis clearly showed the small agglomeration and spherical shape of nanoparticles. SAED pattern also confirms the hexagonal wurtzite structure with single crystalline nature. FTIR analysis showed the vibrational frequency band position of Zn-O shifted to higher frequency band with Co2+ ion increasing host semiconductor nanoparticles. The temperature dependent (300-400 K) DC resistivity of samples was studied by the standard two probe method. DC electrical resistivity was found to increase with increasing Co2+ content in ZnO matrix. The dielectric properties of pure and Co2+ doped ZnO nanoparticles were studied as a function of frequency and composition using the LCR-Q meter. All the dielectric parameters show dispersion and decreases with increase in Co2+ content. The observed dielectric behavior is explained on the basis of Maxwell-Wagner model and Koops phenomenological theory.