Cold Sintered ZnO-Polystyrene\n(PS) Composites with\nModified Interfacial Structures and Properties

Lightweight and integrated electronic devices with high\nperformance\nhave become an inevitable trend in the development of power electronic\nsystems. However, it is challenging to obtain lightweight and miniaturized\nvaristors due to the low threshold electric field. Herein, (1 – <i>x</i>)ZnO-<i>x</i>PS composites with a high threshold\nelectric field are prepared through a cold sintering process at 220\n°C for 50 min, utilizing lightweight PS to modulate the grain\nboundary structures of ZnO varistors. With PS content ≤1.5\nwt %, the relative densities of cold sintered composites exceed 95%.\nPS thin layers with a thickness of 2–10 nm are distributed\nat the grain boundaries of ZnO, forming the Schottky barrier, which\ntriggers nonlinear current–voltage responses. With the addition\nof PS, the threshold electric field is dramatically enhanced from\n135 to 2703 V·mm<sup>–1</sup>, higher than that of commercial\nZnO varistors, which is further demonstrated by the electric field\nsimulation of the Finite Element Method. The interfacial resistance\nobtained from impedance analysis increases with the increase of the\nPS content, and the activation energy of (1 – <i>x</i>)ZnO-<i>x</i>PS composites is higher than that of pure\nZnO ceramics. This study provides a promising approach for the development\nof lightweight and cost-effective varistor materials.