Optimization Of Advanced Piezoelectric Materials Used In High Performance Ultrasonic Transducer

For the purpose of more information was obtained from ultrasound transducer with the development of signal processing but ordinary ultrasound transducer has a high Qm value, narrow bandwidth and limit operating frequency range which was applied in signal receiving and transmitting. In order to design a novel band-width piezoelectric ultrasound transducer with advanced characteristics of transmitting short pulse ease, higher transmission efficiency and temporal resolution, lower system Qm values and acoustic impedance some measures were reported in this paper. Completely and accurately reflect the piezoelectric, dielectric, elastic characteristics of piezoelectric composites material parameters and the loss values in favor of enhance the band-width of ultrasound transducer. Researching the influences between the volume fraction and the width-thickness ratio of piezoelectric phase and electric impedance, bandwidth provide theoretical basis for 1-3 piezoelectric composites transducer design and properties processing research.On one hand, this paper reports a novel piezoelectric material accurate characterization method including loss characteristics, which based upon Simulated Annealing (SA) optimization algorithm and the Least-Square, Which realizes to characteristic the piezoelectric, dielectric, elastic and loss characterization of piezoelectric composite materials. With this method, lead metaniobate and 1-3 piezoelectric composite samples under thickness extensional vibration mode were studied. The optimized electrical impedance resonant characteristics of these samples match the measurement data very well, which verifies that the reported method can precisely characterize piezoelectric materials with loss properties.On the other hand, this thesis realized a novel accurate characterization method for High-Loss piezoelectric material parameters and the loss characteristic, at the same time, analyzing the relationship among the volume fraction , width-thickness ratio of piezoelectric phase and electromechanical coupling coefficient, acoustic impedance, piezoelectric, dielectric, elastic properties, bandwidth, etc; Some theoretical models of 1-3 (4mm symmetry) piezoelectric composite materials based on Newnham series-parallel theory, Hybrid theory, Constitutive relation, Piezoelectric equations were established in this paper; According to the theory models of piezoelectric materials obtain the optimal volume fraction , width-thickness ration of piezoelectric phase, to the greatest extent possible enhancing the bandwidth of transducer; Finally, using the optimal ratio and proportion of piezoelectric phase manufacture 1-3 piezoelectric composite materials and design corresponding wideband transducer.