PhD thesis defense to be held on July 7, 2025 at 10:00 (Multimedia Amphitheater of NTUA)
Thesis title: MATERIALS AND DEVICES FOR HYDROPHONES AND ACOUSTIC DEVICES
Abstract: Acoustic sensors are devices designed to detect sound waves. Sensors that detect sound waves in the air are microphones, and sensors that detect sound waves underwater are hydrophones. Acoustic sensors transform sound waves into electrical signals thus making further analysis possible. Acoustic sensors have a wide range of applications in industry, medicine, and military defense. For example, in the detection of underwater targets, in the study of underwater organisms and ecosystems, and in communications. As part of the preparation of this PhD Thesis, hydrophones were initially developed using commercial piezoelectric discs consisting of Pb(Zr(1−x)Tix)O3 (PZT) of different technical characteristics and dimensions, as sensing elements, and their acoustic response was studied. Following this, an electrical circuit was designed to improve the acoustic performance of the hydrophone and to allow for further processing and analysis on a computer.The hydrophone was calibrated using the method of substitution and its performance was compared to that of commercially manufactured hydrophone in terms of its acoustic response. Last but not least, the sol-gel and solid-state reaction techniques were used to develop barium titanate (BaTiO3) and Ba(1-x)SrxTiO3 (0≤x≤0.8) piezoelectric sensing materials, with the ultimate objective of replacing PZT. These sensor materials can then be used as acoustic sensor elements in sound measurements and hydrophone development. Keywords: Hydrophones, Piezoelectric elements, Hydrophone calibration, PZT, ΒaTiO3, Βa(1-x)SrxΤiO3.
Supervisor: Professor Evangelos Hristoforou
PhD Student: Nefeli Motsi