Synthesis and Structural Study on Co Substituted ZnO Nanoscale Crystals

Abstract

Cobalt substituted ZnO nanopowders with compositional formula Zn_1-xCo_xO (x = 0.00, 0.05 and 0.10) were prepared by co-precipitation method at low temperature. The crystal structure, lattice parameters and average grain size of pure and Co substituted ZnO nanopowders were determined by X-ray diffraction technique. The XRD results indicate that the samples have hexagonal (wurtzite) crystal structure and there is no secondary phases observed. The lattice parameters ‘a’ and ‘c’ decrease with increasing Co content, it may be due the larger ionic radii of Zn²⁺ as compared to the Co²⁺. The X-ray density reduces with increasing Co concentration, indicating the homogeneous substitution of Co²⁺ for Zn²⁺ in wurtzite ZnO structure. The average grain size was estimated from width of XRD using Scherrer's equation, it is observed that the grain size decreases with increasing Co content. The parameter ‘u’ (z coordinate of the oxygen atoms) of the wurtzite structure of Zn_1-xCo_xO increases linearly with increasing Co concentration. The parameter ‘u’ increases as strain increases with Co concentration owing to the lattice distortion.