应力诱发压电薄膜晶内微裂纹演化的数值模拟

Numerical Simulation of the Intragranular Microcracks Evolution in Piezoelectric Thin Films Induced by Stress

压电薄膜的制备和使用过程中不可避免地引入微裂纹等微观缺陷。在不同的内在物理机制和外界驱动力作用下,微裂纹会出现多种多样的形貌演化行为,甚至失稳并发生分裂,影响相关微元器件的各种性能。本文基于表面扩散和蒸发-凝结的经典理论,对应力诱发表面扩散下PZT薄膜晶内微裂纹的演化进行数值模拟。结果表明,在应力作用下,存在临界应力载荷,当应力载荷小于或等于该临界值时,微裂纹演化为稳定的形态;当应力载荷大于该临界值时,微裂纹发生失稳并分裂为多个裂腔,且应力载荷或微裂纹初始形态比的增大均会促进微裂纹的失稳分裂。

During the manufacturing and service process of piezoelectric thin films,microcracks and other micro defects are inevitable.Under the effects of different internal physical mechanisms and external driving forces,microcracks have various morphological evolution behaviors,and even become unstable and split,which influences the performance of related micro components.Based on the classical theory of surface diffusion and evaporation condensation,the evolution of intragranular microcracks in PZT thin films due to surface diffusion induced by stress is simulated.The results show that there is a critical value of stress loading.When the stress loading is less than or equal to the critical value,the microcrack evolves into a stable shape.When the stress loading is greater than the critical value,the microcracks become unstable and split into multiple cavities.The increase of the stress loading or the initial aspect ratio of microcracks promotes unstable splitting.