Electrical characteristics of ZnO–SnO2 composites with emphasis on their frequency dependence as a function of SnO2 content

Abstract

In this experimental work, a well-behaved ZnO-based composite varistor, containing ZnO as a filler and SnO2, high-density polyethylene, and multi-walled carbon nano-tube as additives has been introduced. Samples were prepared using the hot-press method at a pressure of 60 MPa and temperature of 140 °C. Findings indicate that the samples with 92% ZnO have the highest nonlinear coefficient around 21 at the breakdown field of 230.8 × 104(Volt/m). By increasing SnO2 content upto 5%, the breakdown field, nonlinear coefficient, and potential barrier height increase and reach to their maximum values of 230.8 × 104(Volt/m), 21, and 0.71 eV, respectively. However, by further increasing SnO2 content to 8%, these properties decrease. According to the Maxwell-Wagner effect, the frequency-dependent behavior of samples showes that the relative dielectric constant and dielectric loss decrease drastically at frequencies less than 1 kHz. Both parameters show a step-like behavior at the frequency range of 2600–2800 kHz and 4200–5000 kHz.