High Temperature Integrated and Flexible Ultrasonic Transducers for NDT

Integrated (IUTs) and flexible ultrasonic transducers (FUTs) are presented for NDT at high temperatures. These transducers are made of sol-gel sprayed piezoelectric thick (> 40μm) ceramic films. The ceramic materials are lead-zirconate-titanate, bismuth titanate and lithium niobate which are for thickness measurement up to 150°C, 400°C and 800°C, respectively. The IUT can be also deposited onto one end of a long ultrasonic delay line to perform non-destructive testing at the other end at even higher temperatures. FUTs made of bismuth titanate films onto thin stainless steel foils are also used for thickness measurements at 300°C with a high temperature couplant sandwiched between the FUT and a steel substrate. All experiments at high temperatures were performed in pulse-echo and ultrasonic echoes with signal to noise ratios above 20dB were obtained. The centre operation frequencies of both IUTs and FUTs range from 4.4MHz to 10.7MHz.