Piezoelectric micromachined ultrasonic transducers with thick PZT sol gel films

The fabricated micro machined ultrasonic transducers (pMUT) was based on piezoelectric laminated plates operating at flexural modes. The fabricated bimorph pMUT transducers were composed of 5-layers. A 4 μm thick lead zirconate titanate (PZT) thin film deposited by a sol–gel method was used. The piezoelectric layer exhibited a capacitance corresponding to a permitivity of ɛ _r = 1,200. The electromechanical coupling coefficient (k ²) and quality factor (Q) were measured as k ² = 4.4% and Q = 145 in air for a low frequency transducer (240 kHz). The effect of DC bias voltage on frequency and k ² has been studied. The 16.9 MHz transducer yielded values of Q = 25 in air and k ² = 3%.