Piezoelectric Materials at Elevated Temperature

Piezoelectric ceramic patches are the mainstay for actuating and sensing in smart structures, but these patches are limited in the temperature range in which they can operate. Operation at temperatures above ambient is desired for new applications of smart structures, including in aircraft, turbine engine components, space vehicles, and others. The decrease in the actuation and sensing capability with increasing temperature is mainly due to the loss of the piezoelectric properties through depoling. The decrease in performance is also due to the compliance of the adhesive used to bond the patch to the structure, the insulating film covering the patch, and the inside adhesive bonding the film to the wafer. This paper discusses the general properties and modeling of piezoelectric materials, and then experimentally characterizes the performance of piezoelectric ceramic patches used as sensors bonded onto an aluminum beam operating at moderately elevated temperatures. It is shown that the piezoelectric property of the sensor decreases with increasing temperature until the properties are almost completely lost, and also the piezoelectric properties return each time when the sensor is cooled. Finally, high temperature nanotechnology is investigated as an approach that might replace piezoelectric ceramics for sensing and actuating of smart structures at high temperatures.