PbNb2O6 Ceramics with Tungsten Bronze Structure for Low Qm Piezoelectric Material

A broadband ultrasonic transducer was made from [(Pbx,Ba1-x)1-3y/2Lay]Nb2O6 which was prepared by substituting Ba and La for Pb in PbNb2O6. Analysis of the piezoelectric performance as a function of ceramic composition revealed that samples with x=0.40–0.80 and y=0–0.10 have the maximum electromechanical coupling factor (kt). The kt of this sample was 0.45, and the kp was 0.32. Since kp was relatively high with respect to kt, a high-order radial mode appeared in the vicinity of the thickness mode resonance frequency. Slots were cut into both sides of the disk to reduce this phenomenon. The slotted disk had a reduced radial vibration mode, and the kp decreased to 0.06. The kt increased to 0.61, and the mechanical quality factor (Qm) was 20. This ceramic can be used as an efficient broadband transducer.