“Investigation of PMN-32%PT piezoelectric crystals and their application for air-coupled ultrsonic transducers and arrays” Doctoral Thesis

Author, institution: Justina Šeštokė, Kaunas University of Technology

Science area, field: Technology Sciences, Measurement Engineering – 10T

The Doctoral Dissertation is available at the library of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas)

Scientific Supervisor: Prof. Dr. Habil. Rymantas Jonas KAŽYS (Kaunas University of Technology, Technological Sciences, Measurement Engineering, 10T).

Dissertation Defence Board of Measurement Engineering Science Field:

Prof. habil. dr. Arūnas LUKOŠEVIČIUS (Kaunas University of Technology, Technological Eciences, Electrical and Electronic Engineering – 01T) – chairman;
Prof. habil. dr. Tamara KUJAWSKA (Polish Academy of Science, Institute of Fundamental Technological Research, Technological Sciences, Measurement Engineering, 10T);
Prof. habil. dr. Genadijus KULVIETIS (Vilnius Gediminas Technical University, Technological Sciences, Measurement Engineering, 10T);
Prof. dr. Liudas MAŽEIKA (Kaunas University of Technology, Technological Sciences, Measurement Engineering, 10T);
Dr. Egidijus ŽUKAUSKAS (Kaunas University of Technology, Technological Sciences, Measurement Engineering, 10T).

Annotation:

Air-coupled ultrasonic techniques are already used for material characterization, non-destructive evaluation and even for wireless secure transmission of data. The main problem which is met is big losses of ultrasonic signals caused by attenuation and significant mismatch of acoustic impedances of ultrasonic transducers and air. One of the ways to solve this problem is application of composite piezoelectric elements the specific acoustic impedance of which is lower than of monolithic piezoelectric ceramics. Advent of novel piezoelectric materials with a very strong piezoelectric effect such as lead magnesium niobate-lead titanate [PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT)] crystals enables to improve performance of ultrasonic transducers. The properties of the PMN-32%PT crystals may be further improved using domain engineering. The main objective of the dissertation was to analyse and to develop measurement methods of the piezoelectric properties of PMN-PT single crystals during a poling process and to apply those crystals in novel air-coupled ultrasonic transducers and multi-element arrays. A novel measurement technique for simultaneous monitoring of the piezoelectric properties and structural changes of the PMN-32%PT single crystal during poling process has been proposed and successfully implemented. Numerical and experimental analysis of vibrations of piezoelectric PMN–32%PT crystals in steady-state and transient modes. Ultrasonic air-coupled transducers and phased arrays operating in a low frequencies range were developed and investigated both in the transmitting and receiving modes. Selection of the appropriate vibrations modes and optimization of the geometry of PMN-32%PT crystals for air-coupled ultrasonic transducers and arrays.