Stewart, M; Cain, M G; Weaver, P* (2008) Use of Piezoceramics as DC actuators in Harsh environments. In: Actuator 2008, 9-11 June 2008, Bremen, Germany.

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Abstract

Traditionally PZT ceramics have been used as actuators for very precise control of position in scientific equipment such as Atomic Force Microscopes, where the environment is closely controlled. As the applications for these materials become more varied, the actuator materials are being exposed to more aggressive industrial environments, particularly with respect to humidity. This work focuses on the use of PZT ceramics used as DC actuators, and examines the consequences of prolonged exposure to hot and humid environments.

Although the focus of the work is primarily on the piezoceramics it must be recognized that they will always form part of a device and can never be studied without considering electrode materials, coatings and interconnect methods. Whilst coating is often used to protect the materials from humid conditions it is very difficult to completely isolate the ceramic from the environment. This means that it is preferable to engineer the base ceramic and electrode material for maximum resistance to humid conditions, and then use protective coatings to enhance lifetime, rather than protect a system with poor base resistance.

In this work accelerated test methods have been developed to test various material, electrode and coating combinations. Testing has mainly concentrated on the monitoring of the DC conductivity during exposure, but additionally PE loops and strain-field measurements have been carried out on degraded samples. Optical and Scanning Electron microscopy were used to examine the degraded samples, and additionally a new technique for spatially mapping piezoelectric behaviour was used. Scanning LIMM uses an intensity-modulated laser to generate a thermo acoustic signal in a piezoelectric material, and the output response is a pyroelectric current. The laser is scanned in x-y and the current amplitude is plotted as a contour plot of piezoelectric response.

Results of microscopical analysis on the degraded devices will be presented in relation to the degradation mechanism and the various leakage paths discussed. The role of electrode materials and material porosity in the degradation behaviour will also be presented

Item Type:	Conference or Workshop Item (UNSPECIFIED)
Subjects:	Advanced Materials Advanced Materials > Functional Materials
Last Modified:	02 Feb 2018 13:15
URI:	http://eprintspublications.npl.co.uk/id/eprint/4165

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