Application driven industrial development of piezoceramics

Abstract

For more than 40 years, PZT family has been the best established group of piezoelectric ceramics, with a wide variety of compositions, optimised for different applications. It has been divided into hard and soft materials, each of the main groups divided again into subgroups, standardised and widely available in these classical types. The recent developments within the medical field includes, besides 3D diagnostics, new therapeutical applications using high intensity focused ultrasound (HIFU), requires for the latter a hard material type to handle necessary signal level. However, it is also desirable to have, at the same time, higher dielectric constant in order to match electrical impedance. Besides electrical matching, acoustic properties of ceramics are important in order to optimise performance of transducers based on PZT. Mismatch between acoustic properties of PZT and environments, in which transducers have to work, have been overcome by adding matching layers a/o backing and creating composite structure using time consuming and costly dice and fill processes or similar. Finally, high content of lead in PZT has in the light of EU's environmental policy towards sustainable materials, a substantial effort was made to replace PZT by lead free materials. This paper presents, besides two new hard materials with dielectric constant of 1900 and 2800, also an additional version of these materials with engineered structure, where the acoustic impedance has been reduced to approximately15 M Rayleigh. Typical properties for the new materials including lead free ceramics will be presented.