High temperature ultrasonic transducer development by sol-gel composite technique

High temperature ultrasonic transducers have been demanded for some industrial applications, such as process monitoring and structural health monitoring of power/chemical plant. However, there are difficulty to realize such ultrasonic transducers by many reasons, such as space limitation, couplant degradation, complex shapes of monitoring surfaces, backing material degradation/delamination. Ultrasonic transducers made by sol-gel composites could be one of the solutions. The mixture of ferroelectric powders and sol-gel solution is deposited as a film on the target surface, and it becomes porous sol-gel composite film after thermal treatments. Sol-gel composite ultrasonic transducers do not require couplant nor backing material, it could be applied on complex geometry. For sol-gel composite, ferroelectric powder phase material is important, but sol-gel phase material is also important Recently, TiO
2
+SrCO
3
sol-gel phase material has been developed and combined with Bi
4
Ti
3
O
12
and LiNbO
3
powders to realize high temperature ultrasonic transducers. Those sol-gel composites demonstrated superior high temperature performance to existing materials.