Investigation of Microscopic Mechanisms of Failure of Electronic SmartMaterials/Systems

摘要

The development of ferroelectric ceramics is driven by the needs of functionalceramics for various applications, such as sensors, transducers and actuators, and these functional ceramics account for more than 60% of the total high technology ceramics market worldwide. Owing to their strong electromechanical coupling effect and the prompt response to applied electric fields, ferroelectric ceramics have been increasingly used in designing smart actuators for active control applications, such as large flexible space trusses (Crawley and de Luis 1987), fixed wing and helicopter rotary blades (Sprangler and Hall 1990, Samak and Chopra 1993 1994, Giurgiutiu, Chaudhry and Rogers 1994) and automotive suspensions (Thirupathi and Naganathan 1992). The most commonly used ferroelectic ceramics for transducer and actuator applications are the oxides of lead zirconium titanium, Pb(Zr(x)), Ti(1-x)O3, also known as PZT ceramics, because of their strong electromechanical coupling effect and relative low cost for massive production. The actuation force, or the actuation displacement equivalently, is determined by a material parameter, named the remnant polarization which is related to the electromechanical coupling effect of polycrystalline ferroelectric ceramics. The remnant polarization of PZT ceramics deteriorates after many cycles of applied electric field (Jiang, Cao and Cross 1994) and, consequently, the actuation force or the actuation displacement diminishes. This phenomenon, being referred to as electric fatigue, severely restricts the operational life of these actuators. This project focused on the microscopic mechanisms of electric fatigue of ferroelectric ceramics.