Microstructures of the monomorph piezoelectric ceramic actuators with functional gradients

In this paper, a monolithic ceramic bar with a gradient of piezoelectric activity across its thickness is introduced, which is fabricated by interdiffusion between a high piezoelectric and dielectric compositions. The microstructures of the interdiffusion layer have great effects on the electric field-induced displacement characteristics and interfacial strength of the monomorph piezoelectric actuator. The compositional profiles, phase distributions, and short-range phenomena in the interdiffusion layer formed in the PZT/PNN (PbNi1/3Nb2/3O3: PNN) monomorph ceramic actuators with functional gradients are investigated by electron probe microbeam analyses (EPMA) and transmission electron microscopy (TEM), respectively. The results show that the thickness of the interdiffusion layer (d) can be ordered as d(Ni)(2+)>d(Nb)(5+)>d4(Ti)(4+)>d(Zr)(4+). An interface between the rhombohedral and pseudocubic phases is found to exist in the Ni Ti Zr interdiffusion layer by TEM observations and selected area electron diffraction (SAED) patterns. The SAED studies also reveal the presence of the 1/2 [111] superlattice spots along the [111] direction of perovskite cubic unit cell, and the origin of the superlattice is discussed. (C) 1999 Elsevier Science S.A. All rights reserved.