Interface Charge Dynamics and Microstructural Engineering in Multicomponent ZnO Varistors Fabricated via Spark Plasma Sintering for Superior Surge Protection Performance

The operational reliability of ZnO-based varistors—the critical frontline components in electrical surge protection—depends fundamentally on the complex interplay of interface charge phenomena and the microstructural configuration at grain boundaries. In this study, a ten-component ZnO ceramic system was engineered through both conventional sintering and advanced spark plasma sintering (SPS) to systematically investigate the relationship between interface charge dynamics, grain boundary characteristics, and non-ohmic electrical behavior. Guided by the Double-Schottky Barrier model, SPS processing achieved near-theoretical densification (98.7–99.6%), refined and uniform grain sizes of 0.5–2 µm, and elevated potential barrier heights up to 0.95 eV. These microstructural enhancements translated into remarkable performance metrics: nonlinearity coefficients exceeding 50, breakdown voltages reaching 4.8 kV/mm, leakage currents suppressed below 10 µA/cm², and energy absorption capacities surpassing 300 J/cm³. Impedance spectroscopy revealed pronounced grain boundary resistance and shorter charge relaxation times in SPS-processed samples, indicating a faster transient response to surge events. Elemental mapping confirmed the segregation of Bi, Sb, and rare-earth additives at grain boundaries, forming complex intergranular phases responsible for robust barrier formation. The established quantitative framework links interface-state density, grain size, and relaxation dynamics to varistor performance, providing new guidelines for the rational design of next-generation high-stability surge arresters.