HiFFUTs for high temperature ultrasound

Flexural ultrasonic transducers have been widely used as proximity sensors and as part of industrial metrology systems. However, there is demand from industry for these transducers to have the capability to operate in both liquid and gas, at temperatures of 100-200°C and higher, significantly greater than those tolerated by current flexural transducers. Furthermore, flexural transducers tend to be designed for operation up to around 50 kHz, and the ability to operate at higher frequencies will open up new application and research areas. A limitation of current flexural transducers is the electromechanical driving element, usually a lead zirconate titanate piezoelectric ceramic, which experiences significantly reduced performance as temperature is increased. This investigation proposes a new type of flexural transducer, the HiFFUT, a high frequency flexural ultrasonic transducer, comprising a bismuth titanate ceramic for operation at high temperatures, that could be replaced by another suitable high Curie temperature piezoelectric material if required, bonded to the membrane with a high temperature adhesive. The dynamic characteristics of the HiFFUT are studied as a function of temperature, providing insights into its usefulness for industrial applications.