Design And Fabrication Of A Needle Point Hydrophone By Using PMN-PT Single Crystal

The traditional needle point hydrophones have many disadvantages,such as the narrow frequency response of the PZT hydrophone,the low sensitivity of PVDF hydrophone,the high cost of commercial hydrophone.In this study,a novel relaxor ferroelectric single crystal material PMN-PT was selected to fabricate the new needle point hydrophone.The matching materials and simulation method were used to improve its sensitivity and frequency response.Firstly,the impedance of matching layers was obtained by using acoustic theory.Secondly,according to the structure of the design PMN-PT hydrophone,the KLM equivalent circuit of hydrophone was drawn,and the KLM simulation model based on Matlab program was built.The simulation results shown,the sensitivity and bandwidth of the hydrophone were-239.6dB and 2.80?12.08MHz when the matching layer had a 80?m thickness and 4.2 Mrayl acoustic impedance.Its sensitivity was 3.8dB and 18.8dB higher than that of PZT and PVDF hydrophone respectively.And its frequency response was 3.28MHz wider than PZT hydrophone.Finally,according to the simulation parameters of each material,the PMN-PT hydrophone was fabricated,and its performance test system was built up.The results shown that flat frequency response of PMN-PT needle point hydrophone was at 4?12.5MHz,where the sensitivity was up to-238.1dB;At 1.2MHz,its directivity angle of-3dB was 36° and the directivity angle of-6dB was 51°.All the results were quite consistent with the simulation results.