Design and fabrication of high frequency BNT film based linear array transducer

Intravascular ultrasound (IVUS) has been used for diagnosis of coronary diseases. According to the outstanding transducer performance, Ba_0.5Na_0.5TiO₃ (BNT)-based piezoelectric materials are good candidates for the IVUS applications. In this paper, lead-free BNT piezoelectric thick film has been used to fabricate a linear array transducer. The BNT based transducer array has a 2×16-element pattern. In the fabrication process of transducers, micro-machining technologies have been adopted. Wet etching was used to pattern the silicon substrate. The thin layers of Si₃N₄ and SiO₂, are used as etching masks, and patterned by reactive etching and buffered oxide etch (BOE), respectively. After that, the part of Si not covered by the patterned masks is etched by 30% KOH solution. BNT slurry prepared by mixing BNT solution and BNT powder has been deposited on the substrate by spin coating and then thermally treated to obtain the thick film. The PiezoCAD software has been employed to analyze the performance of the array, and the simulation results show that the BNT film array has a center frequency of 82.84 MHz and a -6 dB bandwidth of 46.77%.