Effect of Pressure on Piezoelectric Properties of Relaxor Ferroelectric Solid-Solution Pb[(Mg1/3Nb2/3)0.68]Ti0.32O3 Single Crystal

The piezoelectric properties of a Pb[(Mg 1/3 Nb 2/3 ) 0.68 ]Ti 0.32 O 3 [PMNT(68/32)] binary-system single crystal poled along the [001] direction in the rhombohedral phase were investigated under various pressures up to 400 MPa at 25 °C. The electromechanical coupling coefficient k 33 in the k 33 mode decreased slightly with pressure ( p ). k 31 decreased markedly with increasing p , and decreased by 16% at 400 MPa. The changes in the elastic compliances s 11 E and s 33 E with p were estimated from the changes in resonant frequency [ f r ] and antiresonant frequency [ f a ] with p . s 11 E and s 33 E were 35.4 × 10 -12 and 75.1 × 10 -12 m 2 /N at 400 MPa, respectively. The slight decrease in the mechanical quality factor Q with increasing p in the k 33 mode shows marked contrast to the large decrease in Q in the k 31 mode with increasing p up to 200 MPa. The bandwidth of acoustic devices is proportional to the square of k 33 and is maintained below 400 MPa. Consequently, the PMNT(68/32) rhombohedral single crystal poled along the [001] direction, offering a k 33 of 93% and 10 dB more power under operation at pressures below 400 MPa, is considered to be one of the best candidates from the viewpoint of useful transducer design for ultrasonic devices under water.