High frequency needle ultrasonic transducers based on Mn doped piezoelectric single crystal

doi:10.1016/j.jallcom.2020.154951

Journal of Alloys and Compounds

Volume 832, 15 August 2020, 154951

https://doi.org/10.1016/j.jallcom.2020.154951 Get rights and content

Highlights

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High frequency transducer based on Mn doped PIN-PMNPT single crystals were fabricated and characterized.
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Mn doped PIN-PMNPT transducers show good temperature stability and acoustic properties.
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The Impedance-phase plots of transducer at different temperature are well explained and simulated by Mason model..

Abstract

This paper describes the design, fabrication and imaging application of high frequency needle-type transducers based on manganese doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)-PbTiO₃(Mn: PIN-PMN-PT) piezoelectric single crystals. The grown Mn: PIN-PMN-PT single crystals have a piezoelectric coefficient d₃₃ of 1200 pc/N, an electromechanical coupling factor k_t of 54%, and Curie temperature of 220 °C. Mn: PIN-PMN-PT single crystals based transducers with one and two matching layers show center frequency of 48 MHz, 47.1 MHz and −6 dB bandwidth of 36.7%, 41.8% respectively. Zebrafish have been imaged by these transducers, which shows the potential applications of these Mn: PIN-PMN-PT single crystals based transducers in high resolution biological imaging. Electrical impedance and phase of Mn: PIN-PMN-PT transducers were measured at temperature from 40 °C to 160 °C and the trend of changes was explained by the Mason model in different situations. It was found that the Mn: PIN-PMN-PT can maintain good performance at temperatures as high as 140 °C. The result shows that the Mn: PIN-PMN-PT has superior piezoelectric properties comparable to PIN-PMN-PT and its thermal stability is higher than PMN-PT.

Introduction

Medical ultrasound technologies have been widely developed due to their versatile capabilities in non-radiative, non-invasive, and accurate diagnostic applications [1,2]. As the core element of the medical diagnosis system, ultrasonic transducers with excellent properties fundamentally determine not only the acoustic performance but also the imaging quality. Typically, piezoelectric ultrasonic transducers consist of three main elements: piezoelectric element, front acoustic matching layer, and back acoustic absorbing layer. Among them, the piezoelectric element is key to the quality of the transducers. At present, the piezoelectric materials widely used in high-frequency transducers are mainly (1-x)PbZrO₃-xPbTiO₃(PZT) [3,4] and lead magnesium niobate - lead titanate (PMN-PT) single crystals [5], owing to their high dielectric constants (ε_r³³), high electromechanical coupling coefficients (k₃₃) and high piezoelectric constants (d₃₃). However, PMN-PT single crystals possess a low mechanical quality factor (Q_m = 60), low Curie temperatures (T_c = 140 °C) and a low coercive field (E_c = 2.5 kV/cm) [6] which limits their performance at high-temperature range. Many research dedicated to solving this problem by doping temperature and coercive field in the relaxor-based binary ferroelectric materials such as Pb(In_1/2Nb_1/2)O₃-PbTiO₃ (PIN-PT) [[7], [8], [9]], Pb(Sc_1/2Nb_1/2)O₃-PbTiO₃ (PSN-PT) [[10], [11], [12], [13]], Pb(Yb_1/2Nb_1/2)O₃-PbTiO₃(PYN-PT) [[14], [15], [16]] and Pb(Lu_1/2Nb_1/2)O₃-PbTiO₃(PLN-PT) [[17], [18], [19], [20]]. However, because of the high melting point of the starting chemicals, the progress in the growth of these crystals was very limited.

Recently, the properties of ternary system Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) are of great interest for ultrasound transducers and actuators, offering exceptional high electromechanical coupling (k₃₃ > 0.90), high T_c (180–220 °C) and T_R-T (100–140 °C) [21]. However, PIN-PMN-PT exhibited relatively small Q_m and low coercive field (E_c < 5 kV/cm). To modify the chemical structure and obtain desirable properties, “hard dopant” with other elements provided a new way to harden these materials for higher Qm and larger E_c. For example, Mn doped PIN-PMN-PT (Mn: PIN-PMN-PT) possessed not only has high dielectric constants, high electromechanical coupling coefficients and high electromechanical coupling coefficients but also offers higher Q_m (1000), higher coercive field E_c (∼6 kV/cm) and a higher Curie temperature T_c (∼220 °C) [22,23]. Higher E_c would allow transducers to be driven in a higher electrical field and higher T_R/T for a broader temperature usage range. In this paper, a high-frequency ultrasonic transducer using Mn: PIN-PMN-PT single crystal is designed and fabricated. Transducers with two different designs on matching layer (single matching layer 48.1 MHz and double matching layer 47.6 MHz) are characterized. The imaging quality is examined by the B-mode image of Zebrafish. The high-temperature characterization indicates transducer using Mn: PIN-PMN-PT as the active element exhibits high performance in a broad temperature range. Design and fabrication.

Equivalent circuit software PiezoCAD based on the KLM model was utilized in simulating the performance of Mn-doped PIN-PMN-PT transducer. Fig. 1 shows the structures of the designed transducer with one and two matching layers used for the software program. Two designs on the matching layer are performed for comparison experiments: a single matching layer and a double matching layer with a frequency of approximately 47 MHz and 45 MHz, respectively.

For one matching layer, the acoustic impedance of the matching material (Z_m) satisfies: $Z_{m} = {(Z_{p} Z_{l}^{2})}^{\frac{1}{3}}$

the acoustic impedances of the two matching layers (Zm1 and Zm2) should be respectively equal to: $Z_{m 1} = {(Z_{p}^{4} Z_{l}^{3})}^{\frac{1}{7}}, Z_{m 2} = {(Z_{p} Z_{l}^{6})}^{\frac{1}{7}}$ where $Z_{l}$ and $Z_{p}$ are acoustic impedance of the loading medium and piezo-element, respectively. In this experimental simulation, the front load medium was water, and the rear load medium (backing) was E-solder 3022. The specific design parameters of the transducer and the corresponding material parameter characteristics are summarized in Table 1, Table 2.

The impedance-phase waveform Fig. 2(a) indicated the impedance of Mn-doped PIN-PMN-PT transducer with one matching layer was 40 Ω at 47 MHz. The pulse-echo waveform Fig. 2(b) indicated that the center frequency was 47 MHz and the −6 dB bandwidth is 35.88%. Fig. 3(a) indicated that the impedance of Mn-doped PIN-PMN-PT transducer with two matching layers was 54 Ω at 45 MHz. Fig. 2, Fig. 3 indicated that the center frequency was 45 MHz and the -6dB bandwidth is 55.42%.

Fabricating the ultrasonic transducers based on Mn-doped PIN-PMN-PT according to the above simulation results. The schematic diagram and photograph of the designed Mn-doped PIN-PMN-PT high-frequency ultrasonic transducer with one matching layer are shown in Fig. 3, Fig. 4. Mn-doped PIN-PMN-PT single crystal used as a piezoelectric material was lapped to 40 μm approximately. Cr/Au (50/100 nm) electrodes were sputtered onto both sides. The first matching layer was made by blending Insulcast 501 epoxy (American Safety Technologies, Roseland, NJ) and 2–3 μm silver particles (Sigma-Aldrich Inc., St. Louis, MO), which was cured over the one side of piezoelectric material. The first matching layer was lapped to 9 μm. While for the Mn-doped PIN-PMN-PT transducer with one matching layer, there is no need to cure the silver-epoxy layer. E-solder 3022 (VonRoll Isola, New Haven, CT) was cast over the other side as the backing material and lapped to 1 mm then diced to 0.75 mm × 0.75 mm acoustic stack using a dicing saw (Disco DAD 323). The Polyimide tube with an inner diameter of 1.1 mm and stainless steel hypodermic needle with an outer diameter of 1.62 mm and a length of 40 mm were prepared. The acoustic stack was placed into the Polyimide tube, which provided electrical isolation from the needle housing. A lead wire with an outer diameter of 0.9 mm was connected to the backing layer of the acoustic stack using conductive epoxy (E-solder 3022). The Polyimide tube was put into stainless steel hypodermic needle and fixed with quick-drying epoxy. The gap between the acoustic stack and the stainless-steel hypodermic needle was filled in by insulating epoxy (EPO-TEK 301). Only the matching layer was exposed while the other parts of the acoustic stack were immersed in insulating epoxy. The Cr/Au electrode was sputtered across the first matching layer and stainless-steel housing to form the ground connection (for the Mn-doped PIN-PMN-PT transducer with one matching layer, the electrode was sputtered across the stack and stainless-steel housing). The hypodermic needle was connected and fixed with conductive epoxy (E-solder 3022) to brass housing, which connected to the outer electrode of the SMA connector. The lead wire, which was connected to the backing layer of the acoustic stack, was attached to an inner electrode of the SMA connector. Finally, a thin layer of parylene was vapor-deposited by a PDS 2010 Labcoator (Specialty Coating Systems, Indianapolis, IN) on the top of the first matching layer to serve as both the second matching layer and a protection layer. The thickness of the second matching layer was 9 μm. At the same time, Mn-doped PIN-PMN-PT transducer with one matching layer of parylene (9 μm) was fabricated.

Section snippets

Characterization and discussions

The frequency dependence of electrical impedance and phase plots of Mn: PIN-PMN-PT transducer with one matching layer is displayed in Fig. 5(a), with two match layer is displayed in Fig. 5(b), which were measured by WK6500B 1J65120B impedance analyzer (Wayne Kerr Electronics, UK). The center frequency (f_c) and corresponding impedance (Z) were determined from the plots. As demonstrated in Fig. 5, the resonant and anti-resonant frequency of the Mn-doped PIN-PMN-PT transducer with one protecting

Conclusion

In summary, a high-frequency ultrasonic transducer was designed and fabricated based on Mn: PIN-PMN-PT single crystal. Characterization results show two transducers (one matching layer and two matching layers) with a center frequency of 48.1 MHz or 47.8 MHz and −6 dB bandwidth of 36.7% or 41.8% respectively. Zebrafish imaging was conducted to demonstrate the ability of biological imaging and the high-temperature test shows the usage temperature of this material is at least 60 °C higher than

CRediT authorship contribution statement

Xiao Yang: Formal analysis, Supervision, Software. Zhaoxi Li: Data curation. Chunlong Fei: Project administration, Formal analysis, Funding acquisition, Writing - review & editing. Yangbin Liu: Conceptualization, Investigation. Di Li: Validation, Funding acquisition. Shang Hou: Methodology, Data curation. Lin Zhang: Investigation. Fei Li: Investigation. Yintang Yang: Resources. Qifa Zhou: Resources. Zhuo Xu: Resources.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported in part by the National Natural Science Foundation of China of China under Grant 11604251, in part of the Shaanxi Provincial Association of Science and Technology Young Talents Support Project under Grant 20190105, in part by the National Key Research and Development Program of China under Grant 2017YFC0109703, and in part by the National Key Project of Intergovernmental Cooperation in International Scientific and Technological Innovation under Grant 2016YFE0107900.

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¹: The authors contributed equally to this work.

View full text

High frequency needle ultrasonic transducers based on Mn doped piezoelectric single crystal

Highlights

Abstract

Introduction

Section snippets

Characterization and discussions

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgement

Prog. Mater. Sci.

Prog. Mater. Sci.

Solid State Commun.

Solid State Commun.

Mater. Res. Bull.

J. Cryst. Growth

J. Cryst. Growth

J. Cryst. Growth

Mater. Lett.

J. Inorg. Mater.

Mater. Res. Bull.

J. Alloys Compd.

Ultrasound Med. Biol.

Stretchable ultrasonic transducer arrays for three-dimensional imaging on complex surfaces

Science Advances

Monitoring of the central blood pressure waveform via a conformal ultrasonic device

Nature Biomedical Engineering