PZT-based concave diaphragm transducer with compliant supporting layer for releasing residual stress

This paper presents an innovative fabrication process to produce the PZT-based concave diaphragm transducer. The novel micromachining process builds a concave diaphragm with designed stiffness, curvature, and diameter as the supporting layer of the device. A parylene and heat resistant sealant (RTV) composite is utilized to construct the curved diaphragm with a flexible property. The large stress distribution induced by PZT sol-gel deposition on the compliant diaphragm can be released through the diaphragm curvature change without the PZT film cracking. Based on theoretical evaluation, the residual stresses ranging from 52.5 to 123MPa induced by sol-gel PZT film preparation for different transducer designs in this study are released. The dielectric constant and loss tangent of the deposited film are also investigated. The frequency response of the 5mm diameter transducer that has a radius of curvature of 5mm fabricated with the developed process is further examined. According to laser vibrometer measurement, the device displays the displacement is more than 1.3@mm in air environment and 0.95@mm with 20@mL water loading when driven with sinusoidal waves within a frequency range of 200kHz-1MHz and 40V"p"p.