Broadband Ultrasonic Array Transducer From Multilayer Piezoelectric Ceramic With Lowered Co-Firing Temperature

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 67; no. 5; pp. 968 - 974
• Main Authors: Ke, Qingqing, Liew, Weng Heng, Zhang, Lei, Tan, Chee Kiang Ivan, Jiang, Changyun, Yao, Kui
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.05.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustics; Arrays; Bandwidths; Broadband; Ceramics; Ceramics - chemistry; Circuits; Electrical impedance; Electrodes; Equipment Design; Fabrication; Image quality; Impedance; Insertion loss; Low temperature; Monolayers; Multilayer ceramic (MLC); Multilayers; Nonhomogeneous media; Phantoms, Imaging; piezoelectric; Piezoelectricity; Probes; Signal to noise ratio; Tape casting; Temperature; transducer; Transducers; ultrasonic; Ultrasonic scanners; Ultrasonic testing; Ultrasonography - instrumentation
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2019.2959038

Increasing array transducer bandwidth (BW) and signal-to-noise ratio (SNR) is a critical issue for producing a high-quality medical ultrasound image. However, array elements with small size tend to have poor sensitivity due to a much higher impedance compared with the electrical impedance of the transmitter and receiver circuit. Implementation of multilayer ceramic (MLC) is an effective way of reducing impedance, and thus, with a potential for improving SNR for an ultrasonic probe. In this work, we fabricated multilayer piezoelectric ceramic with a composition of 0.1Pb(Ni 1/3 Nb 2/3 )O 3 -0.35Pb(Zn 1/3 Nb 2/3 )O 3 -0.15Pb(Mg 1/3 Nb 2/3 )O 3 -0.1PbZrO 3 -0.3PbTiO 3 -4mol% excess NiO (PNN-PZN-PMN-PZ-PT), by a roll to roll tape casting process and co-fired with 90Ag/10Pd electrode at a low temperature of 950 °C. Using five-layer MLC (5L-MLC) as obtained, we designed and demonstrated a 5 MHz 32-element array transducer for ultrasonic and photoacoustic imaging. The five-layer transducer element exhibited a BW of 87% at −6 dB, substantially higher than 62% for single-layer ceramic (SLC) element. In addition, the insertion loss was improved by 16.2 dB over the SLC element with an external impedance of <inline-formula> <tex-math notation="LaTeX">50~\Omega </tex-math></inline-formula>. Both the experimental results and theoretical analysis showed that our array transducer made of the PNN-PZN-PMN-PZ-PT MLC is promising for acquiring high-quality ultrasonic and photoacoustic images.