Ferroelectrically Hard Porous Ceramics: Fabrication, Properties and Ultrasonic Transducer Applications

摘要

New family of porous ceramics, based on ferroelectrically hard PZT compositions with properties, combining better parameters of PZT ceramics and 1-3 composites for high intensity ultrasonic applications, are developed. The fabrication methods, measurement techniques, and the results of experimental study of ferroelectrically hard porous piezoceramics are described. The physical justification of the applicability of porous ceramics for high intensity focused ultrasound applications (HIFU), as well as HIFU transducers designs, the results of acoustics field measurements, and the results of ex vivo experiments on biological tissues are also presented. Developed ferroelectrically hard porous piezoceramics are characterized by increased values of piezoelectric and electromechanical coupling factors, reduced values of acoustic impedance and lateral parasitic modes of vibration, as well as better resonance characteristics compared to dense piezoceramic elements. Moreover, porous piezoceramics elements are easily processed, more stable against thermal and mechanical influences and provide higher adhesion of electrodes in comparison with standard dense piezoceramic and composite elements that makes it prospective materials for high power ultrasonic applications. It was shown that the use of ferroelectrically hard porous ceramics simplifies the manufacturing process, allows one to increase the main operational characteristics of HIFU transducers and makes them competitive in comparison with the standard ultrasonic transducers for promising applications in the field of medical therapy.