Yan Peng, Si Mingming, Liu Yongping, Ren Yu, Ding Qi, Jiang Weizhong, Fan Yuchi, Jiang Wan
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Institute of Functional Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China.
Nat Commun. 2024 Nov 12;15(1):9812. doi: 10.1038/s41467-024-54279-x.
The modulation of the electrostatic potential barrier at grain boundaries determines the performance of many ceramic-based electronics such as varistors. However, conventional protocols relying on complex doping and annealing processes inevitably increase the inhomogeneity of microstructure, which may jeopardize the performance stability and mechanical reliability in service. Instead of doping, herein we demonstrate an effective strategy to modulate the potential barrier in ZnO-based low-voltage varistors by exploiting internal stress-induced piezoelectric polarization. The local residual stress as large as ~1 GPa can be created in the ZnO matrix by incorporating ultra-stiff nanodiamond particles using a cold sintering process. As a result, the composite with only 2 wt% of nanodiamond exhibits a prominent nonlinear current-voltage response at a low switch voltage of 15.7 V/mm, which is ascribed to the depressed barrier height induced by the distinct effects of positively and negatively charged polarization on grain boundaries. More strikingly, the large internal stress can significantly enhance the strength of the composite by more than 230% compared with the monolith, owing to the highly strengthened grain boundaries and crack-tip bridging from prestressed nanodiamonds. These findings add internal stress as a new dimension to design mechanically robust ceramic electronics with high performance.
晶界处静电势垒的调制决定了许多基于陶瓷的电子产品（如压敏电阻）的性能。然而，依赖复杂掺杂和退火工艺的传统方法不可避免地会增加微观结构的不均匀性，这可能会危及器件在服役时的性能稳定性和机械可靠性。本文不采用掺杂方法，而是展示了一种通过利用内应力诱导的压电极化来调制基于ZnO的低压压敏电阻中势垒的有效策略。通过冷烧结工艺掺入超硬纳米金刚石颗粒，可以在ZnO基体中产生高达约1 GPa的局部残余应力。结果，仅含有2 wt%纳米金刚石的复合材料在15.7 V/mm的低开关电压下表现出显著的非线性电流-电压响应，这归因于正负电荷极化对晶界的不同作用所导致的势垒高度降低。更引人注目的是，由于晶界的高度强化以及预应力纳米金刚石的裂纹尖端桥接作用，与整体材料相比，大的内应力可使复合材料的强度显著提高超过230%。这些发现为设计具有高性能的机械坚固的陶瓷电子产品增添了内应力这一新维度。
