Non-linear Electrical Characteristics of ZnO Modified by Trioxides Sb2O3, Bi2O3, Fe2O3, Al2O3 and La2O3

Abstract

The non-linear behavior of polycrystalline-ZnO-based voltage-dependent resistors is considered in the present study. A high-temperature solid-state reaction route was used to synthesize polycrystalline samples of ZnO modified by small amounts of the trioxides Sb2O3, Bi2O3, Fe2O3, etc. in various proportions. X-ray diffraction and scanning electron microscopy techniques were used to study the structural and microstructural characteristics of modified ZnO. Detailed studies of non-linear phenomena of the I–V characteristics, dielectric permittivity (er), impedance (Z), etc. of the samples have provided many interesting results. All the samples exhibited dielectric anomaly. Non-linear variation in polarization with electric field for all the samples was observed. Moreover, significant non-linearity in the I–V characteristics was observed in the breakdown region of all the samples at room temperature. The non-linear coefficient (α) in different cases, i.e. for I–V, er–f, er–T, and er–Z, was calculated and found to be appreciable. The frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law.