RESEARCHERS FOCUSED ON PHYSICAL PROPERTIES
Synthesis and Processing of Multilayer Ceramic Actuators: Lifetime Assessment
Multilayer ceramic actuators (MCAs) are devices which are constructed from an electrostrictive, lead-magnesium-niobate ceramic material (PMN). When a voltage is applied to the actuator, large deformations under load may be obtained. Unlike most piezoelectric ceramics, the electrostrictor PMN exhibits low hysterisis when cycled and does not suffer irreversible changes under large applied voltages. However, owing to the construction of the actuator, failure of the device may occur relatively early in the desired lifetime of the actuator.
MCAs are constructed using multiple layers of PMN with electrodes between each layer. As a result of the differing properties between the ceramic and the electrode, cracking in the ceramic and delamination of an electrode from the ceramic may occur during extended electromechanical stressing of the actuator. It is the purpose of this study to investigate whether or not various nondestructive evaluation techniques may be used to identify actuators which will fail prematurely as a result of extended stress cycling.
In this study, nondestructive evaluation techniques which are known to be sensitive to microstructural flaws will be used to monitor a number of actuators which will be electromechanically stressed to failure. These techniques will be used to identify the failure mechanisms involved and will also be used to determine whether or not the actuators which fail prematurely may be identified before any cycling has occurred.
Practical Application
MCAs contain intrinsically low-cost materials, yet have labor intensive and costly processing which limit their use. Development of in-process quality control and reliability testing will contribute to advanced synthesis and processing of reliable, low-cost actuators.
