Effect of Al 2 O 3 Transition Layer Thickness on the Microstructure and Ferroelectric Properties of Lead Zirconate Titanate

In order to avoid the deterioration of the electrical properties of the lead zirconate titanate (PZT) coating due to the poor bonding performance between the PZT coating and the metal substrate, an Al 2 O 3 layer is introduced as a transition layer between the PZT coating and the metal substrate. It is found that the failure of the PZT/Al 2 O 3 structure depends on the size of the transition layer. Scanning electron microscope (SEM) results show that as the transition layer thickness increases beyond 90 μm, cracks appear in the coating, and the crack direction is perpendicular to the PZT/Al 2 O 3 interface. With the increase in thickness, in addition to the cracks perpendicular to the PZT/Al 2 O 3 interface, cracks parallel to the interface also appeared in the coating. X-ray diffraction (XRD) results show that the PZT coating samples have a typical perovskite structure, and their crystallinity is negatively correlated with Al 2 O 3 thickness. With the increase of the transition layer thickness, the electrical properties of PZT/Al 2 O 3 gradually decrease. Piezoelectric force microscope (PFM) results show that the amplitude response decreases with increasing Al 2 O 3 thickness. When the Al 2 O 3 thickness is 110 μm, the energy loss during the polarization process is the most significant. The residual stress results show that different sizes of Al 2 O 3 transition layers provide different initial stress conditions for the PZT/Al 2 O 3 structure. The initial compressive residual stress increases with increasing Al 2 O 3 layer thickness. It changes the stress distribution at the interface and provides a driving force for crack growth, and the structural integrity of the PZT coating is damaged. The phase results show that the domain size of the PZT coating increases with the increase of the Al 2 O 3 layer size, which may be due to the peeling between PZT and Al 2 O 3 , which makes the PZT layer not completely constrained by the matrix, and the domain size of the PZT coating increases.