Cold sintered composites consisting of PEEK and metal oxides with improved electrical properties via the hybrid interfaces

The manipulation of interfacial structures offers an effective route to improve the physical and chemical properties of materials. However, it is challenging to design ceramic-based composites with hybrid interfaces involved with organics and inorganics through the conventional sintering technique, due to the incompatibility of these materials at high temperatures. Here, we propose a strategy to integrate poly-ether-ether-ketone together with several metal-oxide additives into zinc oxide (ZnO) to form composite varistors via cold sintering process. Nanoscale layers of hybrid additives are dispersed between densified ZnO grain structures forming Schottky barriers, which dramatically improves the electrical properties of the resulted composites. Compared with pure ZnO, the breakdown electric field at 0.1 mA mm⁻² reaches over 13 kV mm⁻¹. Particularly, the composite shows a switch-like effect similar with switching devices, with an extraordinarily high nonlinear coefficient of 375. In addition, the elastic module decreases with the addition of PEEK. Given the flexibility in the dopants of polymers and metal oxides, this work provides a unique route to design composite materials with superior performances.