Role of oxygen vacancy on the electrical properties of SnO2-Zn2SnO4 ceramic composites with the introduction of Nb2O5 oxide

In this work, the role of oxygen vacancy on the electrical properties of traditionally prepared SnO2-Zn2SnO4 ceramic composites was evaluated by introducing Nb2O5 oxide. With increasing Nb2O5 content, the breakdown electric field E1.0 and the relative permittivity εr measured at low frequencies increased and declined, respectively. In the microstructure photos, the grain size decreased before reaching a saturation point. In addition, Nb was randomly distributed in the grains and along grain boundaries. By doping Nb2O5, the color of the sintered samples darkened, and F-type color centers were generated. In the complex electric modulus spectra, the peak of the imaginary part M″ shifted toward a lower frequency; whereas, the activation energy Ea changed slightly with increasing Nb2O5 content. The results suggest that oxygen vacancy is the origin of the varistor and high permittivity properties of SnO2-Zn2SnO4 ceramic composites. Furthermore, the varistor and dielectric properties can be modulated by changes in the microstructure.