High-performance ultrasonic transducer based on PZT piezoelectric ceramic for high-temperature NDE.

Piezoelectric ultrasonic transducers (PUT) are applied in a wide range of fields such as non-destructive evaluation (NDE), medical imaging and petroleum exploration, etc. Nevertheless, most PUTs cannot achieve high performance and high operating temperatures simultaneously because of the inverse correlation between piezoelectric property and operating temperature. In this paper, a high-performance ultrasonic transducer based on PZT-5A type piezoelectric ceramic (S35) for high-temperature NDE over 300 °C was proposed. Firstly, it is found that the d33, kp, and kt of the S35 ceramic plate show great temperature stability from 50 °C to 300 °C, which is attributed to the stabilisation of the phase structure and no occurrence of obvious depolarization behavior before the Curie temperature. And then, a single-element PUT based on S35 was fabricated, and pulse-echo tests from 50 °C to 300 °C in confined heating environments were executed. The peak-to-peak value (Vpp) varies from 2.58 V to 0.753 V, which results from the increase of the permittivity of the piezoelectric element and the degradation of the acoustic contact, and the -6dB BW demonstrates excellent temperature stability with a variation less than 10%. These results indicate the great potential of this high-performance ultrasonic transducer for high-temperature NDE.

Broadband and high sensitive time-of-flight diffraction ultrasonic transducers based on PMNT/epoxy 1-3 piezoelectric composite.

5-6 MHz PMNT/epoxy 1-3 composites were prepared by a modified dice-and-fill method. They exhibit excellent properties for ultrasonic transducer applications, such as ultrahigh thickness electromechanical coupling coefficient k(t) (85.7%), large piezoelectric coefficient d33 (1209 pC/N), and relatively low acoustic impedance Z (1.82 × 107 kg/(m2·s)). Besides, two types of Time-of-Flight Diffraction (TOFD) ultrasonic transducers have been designed, fabricated, and characterized, which have different matching layer schemes with the acoustic impedance of 4.8 and 5.7 × 106 kg/(m2·s), respectively. In the detection on a backwall of 12.7 mm polystyrene, the former exhibits higher detectivity, the relative pulse-echo sensitivity and -6 dB relative bandwidth are -21.93 dB and 102.7%, respectively, while the later exhibits broader bandwidth, the relative pulse-echo sensitivity and -6 dB relative bandwidth are -24.08 dB and 117.3%, respectively. These TOFD ultrasonic transducers based on PMNT/epoxy 1-3 composite exhibit considerably improved performance over the commercial PZT/epoxy 1-3 composite TOFD ultrasonic transducer.

Fabrication of a PMN-PT single crystal-based transcranial Doppler transducer and the power regulation of its detection system.

Doppler sonographic measurement of flow velocity in the basal cerebral arteries through the intact skull was developed using a pulsed Doppler technique and 2 MHz emitting frequency. Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) were chosen to be the piezoelectric transducer material due to their ultrahigh piezoelectric coefficients, high electromechanical coupling coefficients and low dielectric loss. The pulse-echo response of the transducer was measured using the conventional pulse-echo method in a water bath at room temperature. The -6 dB bandwidth of the transducer is 68.4% and the sensitivity is -17.4 dB. In order to get a good match between transducer and detection system, different transmission powers have been regulated by changing the impedance of the transmitting electric circuit. In the middle cerebral artery (MCA) measurement photograph results, as the transmission power is increasing, the detection results become clearer and clearer. A comparison at the same transmission power for different transducers shows that the detection photograph obtained by the crystal transducer was clearer than that obtained with a commercial transducer, which should make it easier for doctors to find the cerebral arteries.

High performance relaxor-based ferroelectric single crystals for ultrasonic transducer applications.

Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed.