软模板法制备高频超声换能器用1-3复合压电材料

Fabrication of 1-3 Piezocomposites via Soft Mold Method for High-frequency Ultrasound Transducer

医用高频超声成像技术广泛应用于皮肤、眼睛及血管壁等人体组织的精细结构成像。1-3复合压电材料因具有较高的机电耦合系数而成为高频超声换能器的核心材料。传统的机械切割-填充、等离子蚀刻等1-3复合材料制备方法成本高、效率低,难以实现工业化制备。本研究提出一种新的基于软模板的高频复合材料制备方法,在获得高机电耦合系数的同时,实现高性能1-3复合压电材料的低成本制备。研究采用微米孔径的软模板实现PZT粉的浆料填充,通过热压烧结获得均匀竖立的PZT陶瓷微柱阵列,进而制备出PZT/环氧1-3复合材料。对复合材料进行系统的机电性能测试,并利用不同方法对复合材料的微结构及其均匀性进行表征。结果表明,软模板法可使压电微柱具有完整的相结构和较高的成分均匀性,能够实现较高的胚体压缩率,提高陶瓷微柱的致密度,同时形成了微柱阵列且微柱直径可控制在70μm。软模板法有利于在提高复合材料超声频率(30~50 MHz)的同时获得64%的高机电耦合系数,为医用高频超声成像以及超声生物显微镜等应用提供了一种高效的1-3复合压电材料工业化制备方法。

The high-frequency ultrasonic technology has been widely used for the fine structures medical imaging of skin, eye and vessel as its high spatial resolution. 1-3 piezocomposite plays an important part in the high frequency transducer owing to the excellent electromechanical coupling properties of this material even at high frequency. However, its industrial applications were limited by the inefficient fabrication methods and expensive equipment, such as mechanical cutting-filling and plasma/laser etching. In this work, a low-cost and novel soft mold method was developed to fabricate 1-3 piezoelectric composites with high electromechanical coupling coefficient kt for high frequency ultrasound transducers. The process of soft mold filling, hot-pressed sintering PZT pillars and epoxy curing was ruly carried out. Then, a series of samples with different thicknesses were fabricated and characterized. It demonstrates that the fabricated PZT pillars with pure rhombohedral phase are homogeneous.Besides, the length to diameter ratio of sintered pillars is 10 : 1 and the k_(t) of the 1-3 piezocomposite reaches as high as 64% for the 30-50 MHz high frequency transducer. The result indicates that the soft mold method is an economical and effective way to fabricate the 1-3 piezoelectric composites for medical and biological imaging in high frequency ultrasound applications.