Fabrication and characterization of annular-array, high-frequency, ultrasonic transducers based on PZT thick film

In this work, low temperature deposition of ceramics, in combination with micromachining techniques have been used to fabricate a kerfed, annular-array, high-frequency, micro ultrasonic transducer (with seven elements). This transducer was based on PZT thick film and operated in thickness mode. The 27 mu m thick PZT film was fabricated using a low temperature (720 degrees C) composite sol-gel ceramic (sol + ceramic powder) deposition technique. Chemical wet etching was used to pattern the PZT thick film to produce the annular array ultrasonic transducer with a kerf of 90 mu m between rings. A 67 MHz parallel resonant frequency in air was obtained. Pulse-echo responses were measured in water, showing that this device was able to operate in water medium. The resonance frequency and pulse-echo response have shown the frequency response presented additional resonance mode, which were due to the lateral modes induced by the small width-to-height ratios, especially for peripheral rings. A hybrid finite-difference (FD) and pseudospectral time-domain (PSTD) method (FD-PSTD) was used to simulate the acoustic field characteristics of two types of annular devices. One has no physical separation of the rings while the other has 90 mu m Iced between each ring. The results show that the kerfed annular-array device has higher sensitivity than the kerfless one. (C) 2014 Elsevier B.V. All rights reserved.