Thermally assisted cold sintering of high-performance ZnO-based varistor ceramics: Effect of Dy2O3

Developing ZnO-based varistor ceramics with high breakdown field and large nonlinear coefficient remains a great challenge. To address this issue, a thermal-assisted cold sintering process was employed to densify ZnO-based varistor ceramics at 300 °C and enhance their electrical properties through an annealing process at 900 °C. The pivotal roles of Dy 2 O 3 in tailoring the microstructure and electrical properties have been systematically studied. It is found that doping of Dy 2 O 3 suppresses ZnO grain growth, reducing the average grain size from 3.23 μm to 2.21 μm. Simultaneously, it introduces deep-level defects and increases interface state density, significantly elevating the Schottky barrier height from 1.74 eV to 3.15 eV. Specifically, the ZnO-based varistor ceramic with 0.5mol% Dy 2 O 3 presents a high breakdown field of 990 V/mm, with a large nonlinear coefficient of 109, and an ultralow leakage current density of 0.07 μA/cm 2 . This work provides an energy-efficient route for developing high-performance ZnO-based varistor ceramics.