Design Of High Frequency Spherical Single Element Ultrasonic Transducer Based On 1-3 Piezoelectric Composite

The ultrasonic transducer is one of the most important component in medical ultrasonic imaging apparatus, and which still has a number of technical bottlenecks could not break through. The ultrasonic transducer based on the 1-3 type piezoelectric composite material has a great advantage in the traditional single crystal material. It has the advantages of low acoustic impedance, small dielectric constant, large bandwidth value, high electromechanical conversion efficiency, etc. The spherical ultrasonic transducer without adding lens to focus, which reduces the loss of energy in the process of ultrasonic transmission, and an excellent characteristics of acoustic field can be obtained. Overall, this ultrasonic transducer not only has a good beam performance, but also has a high resolution and sensitivity.First, the concept and background of ultrasonic transducer, spherical single element ultrasonic transducer and piezoelectric composite material are introduced in this paper. By analyzing the present situation of domestic and international development, the research content and significance are discussed and the technical route of high frequency spherical single-element ultrasonic transducer based on 1-3 type piezoelectric composite material is put forward in this paper.Secondly, the paper introduces the theory of piezoelectric composite materials and pressure acoustic correlation. For the first time, the finite element model of 1-3 type piezoelectric composite material and spherical transducer was established by using COMSOL software. Through simulation analysis, the parameters of the piezoelectric composite material and the thickness of the matching layer for the transducer are optimized, and the acoustic field characteristics of the transducer are studied.Subsequently, taking the optimized parameters of 1-3 type piezoelectric as the theoretical basis, and the composite materials are prepared by the improved cutting method. The surface electrodes were prepared by magnetron sputtering method, and the characterization of the materials was analyzed. The relative permittivity, electromechanical coupling coefficient, acoustic impedance, and longitudinal wave velocity of the 1-3 type piezoelectric composite material are obtained, and the results are compared with the simulation results.Finally, using the sample of 1-3 type piezoelectric composite material as the foundation and the optimized parameters of transducer simulation design as the instruction to fabricate high frequency spherical single-element ultrasonic transducer based on 1-3 type piezoelectric composite material. Through the research on the traditional technology and a new solution is proposed, which makes the process more reliable and easy to operate. The center frequency, bandwidth and focal length of the transducer sample are basically meet the expected design index through the pulse echo experiment.Through the above research, the results of the COMSOL finite element simulation analysis accord with the experimental results, and the filler of the kerf, the composite aspect-ratio and the thickness of the matching layer have a great influence on the performance of the piezoelectric composite material and the transducer. A new method for the simulation of 1-3 type piezoelectric composites and the simulation design of transducer are provided in this paper, and a new method for the preparation of spherical single-element ultrasonic transducer is designed. This paper lay a firm foundation for the further study of the composite ultrasonic transducer, and it can also provide reference for designing other transducers.