多层独石式压电微位移器的扫描电声像研究

STUDY ON SCANNING ELECTRON ACOUSTIC IMAGING OF MONOLITHIC MULTILAYER PIEZOELECTRIC ACTUATOR

对多层独石式压电微位移器的陶瓷／内电极层界面进行扫描电子显微镜（ＳＥＭ）和扫描电声显微镜（ＳＥＡＭ）的无损观察，发现该界面在ＳＥＭ和ＳＥＡＭ下观察得到的像所给出的信息存在着很大差别。根据ＳＥＡＭ的成像原理、探针能谱分析（ＥＤＳ）以及器件本身陶瓷／内电极层间的层状结构形式，认为这种差异是由于器件在热压和烧结等制作过程中，陶瓷层和内电极层间不同的收缩率使得界面产生非均匀性力学性能而引起的，它与器件烧结时陶瓷与内电极间界面的残余热应力有关。该热应力也是器件烧成时陶瓷与内电极分层以及部分器件在加电压应用时沿界面产生分层现象的一个重要原因。

Monolithic multilayer piezoelectric actuator was tested by two nondestructive methods, scanning electron microscopy (SEM) and scanning electron acoustic microscopy (SEAM). The SEAM image of the ceramics/internal electrode interface region was found much wider than the SEM image. Based on the SEAM imaging mechanism, the results of EDS analysis and the layer structure of the actuator, this effect was interpretted as being resulted from the large thermal internal stress at the interface between ceramics and the internal electrode. The thermal internal stress is induced by the different thermal contraction during preparation of actuator using thermal pressure and cofiring process, and is the cause of delamination for some actuators during cofiring or under an applied voltage in application.