Dielectric polarization and electrical properties of Modified PbTiO₃Piezoelectric Ceramics for high frequency transducer applications

Abstract

IntroductionNowadays, high frequency transducers have been widely used in underwater sound equipment of high frequency and high resolution such as three-dimensional imaging sonar, multi-beam sounding sonar, ocean current profiler, side-scan sonar and anti-frogman sonar, etc. They are core functional devices in fields like small target detection and precise imaging. The performance parameter of piezoelectric materials that satisfy applications of high frequency transducers should be provided with low dielectric constant and low dielectric loss. As a critical factor to the performance of transducers, the dielectric loss of piezoelectric materials can not only determine the energy consumption of transducers, but also influence all kinds of other performances of transducers (such as mechanical quality factor Q value and waveform characteristics of transducers, emission/reception efficiency of sonar systems, stability and heat effect of transducers, etc.). Impedance mismatch is one of the main factors of giving rising to system energy consumption and cutting emission/reception efficiency. In electric circuits, the equivalent impedance of devices Z=d/2πfεs (d and s represents thickness and superficial area of devices respectively, and f represents working frequency, ε dielectric constant). For certain impedance, only relatively low dielectric constants can better meet impedance matching at high frequency of utilization.With regard to piezoelectric materials, the domain which gives it piezoelectric properties will bring about extra relaxation polarization, and thus dielectric constant and dielectric loss will be increased. Therefore, the dielectric constant of most piezoelectric materials is all above 1000, and dielectric loss