Influence of Cr incorporation on structural, dielectric and optical properties of ZnO nanoparticles

• Cr doped ZnO nanoparticles were synthesized by low cost sol–gel method.
• Crystallite size of ZnO is found to decrease with increase in Cr dopant.
• Frequency depended dielectric study was carried out at room temperature.
• Dielectric results have been explained by Maxwell–Wagner model and Koops theory.
• A reduction in band gap of ZnO with increase in Cr content.

This study demonstrated the effect of Cr doping on structural, dielectric and optical behavior of ZnO nanoparticles synthesized through sol–gel method. Characteristic investigations have been carried out by X-ray diffraction, Field emission scanning electron microscope, Energy dispersive X-ray spectrometry, and Transmission electron microscope. The results confirmed the formation of nanoparticles in polycrystalline single phase with hexagonal wurtzite structure. The crystallite size has been found to vary around 20 nm. Dielectric studies were carried out by Impedance spectroscopy. The decrease effect of dielectric parameters with increase in dopant has been explained on the basis of Maxwell–Wagner model and Koops phenomenological theory. The impedance analysis suggested that the contribution of grain boundaries is dominating over grain contribution. A red shift in UV–vis spectra signified that band gap can be tuned by Cr doping from 3.32 to 3.22 eV because of the s–d and p–d exchange interactions.

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