Less gives more: on the optimal filling fraction of piezoelectric acoustic power receivers

In this paper, we investigate the suitability of 1-3 composite transducers as receivers in acoustic power transfer applications. In contrast to the commonly used PZT transducers, the composites allow us to modify the acoustic impedance, the losses and the electromechanical coupling factor, and hence analyse their influence on the efficiency of acoustic power receivers. Comparing composite receivers with 40%, 60% and 80% filling factors, we find that the lowest filling fraction gives the highest efficiency. This is due to its lower acoustic mismatch with water, which compensates its lower electromechanical coupling and mechanical quality factor.