Fig. 3: Nonlinear current-voltage behavior.
a Current density-electric field (I-V) curves of ZnO and composites under different sintering pressure, inset is the enlarged part of dashed square showing mild nonlinearity in monolithic ZnO. b I-V curve of cold sintered composites with α-Al2O3 and various ND contents. c Measured switch voltage (Es at 0.1 mA/mm2) and nonlinear coefficient for various samples prepared in this study. d Nyquist plots of cold sintered samples under different sintering pressures. e Experimentally determined potential barrier height as a function of internal stress of ZnO matrix; inset is the Arrhenius type plot of the resistivity ρ, where the values of ρ were extracted at a frequency of 10 Hz from temperature-dependent impedance measurements. f Comparison of performance for ZnO-based binary-system (single dopant) varistors and the ZnO composites with soft and rigid second phases18,19,36,37,38,39.
