Head of group, Tomás Gomez, will give a talk at the Physical Acoustics Tutorial Day: Ultrasound Generation and Detection, 21 September 2018,organized by Institute of Physics, London, UK. LINK. Registration is still open!
Title: Piezoelectric transduction and air-coupled ultrasound.
This talk reviews the basic concepts of piezoelectricity starting from a macroscopic thermodynamic definition of the phenomenon, showing that this is one particular case of what we call, in general, coupled systems. Then, its microscopic origin is reviewed. In this context, a brief historical review of the advances in piezoelectric materials is presented starting from initial piezoelectric crystals, and then going through some of the main milestones like ferroelectric ceramics, epoxy-ceramic composites, textured ceramics, relaxor ferroelectric single crystals, lead-free ceramics, etc.
Then, the question of how to make use of this material property to build an useful transducer to generate and receive ultrasonic signals is addressed and several examples are considered (medical ultrasound, SAW devices, distance and presence sensors, etc.)
Finally, one of the most demanding problems in the field of design and fabrication of piezoelectric ultrasonic transducers is considered: air-coupled transducers. This give us the opportunity to have a closer look at other transducer components, apart from the piezoelectric element, that are also important and that, in this particular application, become critical, like electrical matching, backing blocks, acoustical impedance matching, mode decoupling and advanced optimization techniques.