Super-Cell Piezoelectric Composite With 1-3 Connectivity.

Abstract

The standard fabrication method for 1-3 piezocomposites for ultrasound transducers is the "dice and fill" method (DFM) in which lateral periodicity is introduced. This contributes to the appearance of spurious modes that can drastically affect the performance of the device if they appear near its thickness mode frequency, thus limiting the effective frequency range. A new 1-3 piezocomposite fabricated with a super-cell structure [1-3 super cell (13SC)] was designed in order to overcome these limitations. It consists of the merging of several periodic cells with 47% PZT volume fraction and epoxy resin as the matrix. Two lateral periodicities in one direction are defined as well as two different kerfs. The chosen cell shape is composed of five nonaligned square section rods ( 1 ×1 mm 2 ). For comparison of performance, two regular 1-3 piezocomposites (the same materials and equivalent periodicities) were fabricated by DFM. Electroacoustic responses in water were measured for the three composites being considered as transducers. Successive regular thinnings (from 2.8 to 1.1 mm) were carried out for each sample to increase the operating frequency (from around 0.4 to 1.3 MHz) and study the evolution of the characteristics (bandwidth and sensitivity). The experimental results confirmed the behavior of those obtained with numerical simulations, showing that the 13SC composite can be used in this entire frequency range, unlike regular composites.