FEM simulation and comparison of PMN-PT single crystals based phased array ultrasonic transducer by alternating current poling and direct current poling

doi:10.1016/j.ultras.2020.106175

Ultrasonics

Volume 108, December 2020, 106175

https://doi.org/10.1016/j.ultras.2020.106175 Get rights and content

Highlights

•
The ACP phased arrays have a higher k_eff compared to DCP arrays.
•
The coupling effect of transverse vibration for ACP arrays is weaker.
•
The crosstalk of the ACP arrays is 0.91 dB lower than that of DCP arrays.
•
The ACP arrays is 7.2% broader bandwidth compared to the DCP arrays.
•
The ACP arrays is 0.79 dB higher relative sensitivity compared to the DCP arrays.
•
The max acoustic pressure of ACP arrays is 13.8% higher than that of DCP arrays.

Abstract

The Finite element modeling (FEM) simulation and comparison of electroacoustic properties for alternating current poling (ACP) phased arrays and direct current poling (DCP) phased arrays were investigated. The simulated electrical impedance reveals that the effective working bandwidth of ACP phased arrays is wider than that of DCP phased arrays as a whole. Besides, the ACP phased arrays have a higher effective electromechanical coupling coefficient k_eff compared to DCP arrays, which indicates that higher electromechanical conversion capacity is obtained. The average value of the ratio of longitudinal displacement R_disp for ACP phased arrays is larger than that of DCP arrays, indicating that the longitudinal transmission efficiency of acoustic energy can be enhanced by using the ACP method. The simulation results of crosstalk are consistent with the results of vibration modal analysis. The coupling effect of transverse vibration for ACP phased arrays is weaker than that of DCP arrays, leading to reduce the interaction between the adjacent elements. The crosstalk of the ACP arrays is −11.87 dB, 0.91 dB lower than that of DCP arrays. The pulse-echo response of ACP phased arrays is 7.2% broader −6 dB bandwidth, 0.79 dB higher relative sensitivity compared to the DCP phased arrays, which prove that the longitudinal resolution and penetration depth of the ultrasonic imaging can be improved by using the ACP arrays. Besides, the consequences of the beam profile illustrate that the maximum acoustic pressure of ACP arrays is 13.8% higher than that of DCP arrays and the directivity of ACP array is slightly better than that of DCP arrays.

Introduction

Ultrasound transducer has become much wider used for clinical diagnosis technology such as ophthalmology, cardiology, and intravascular applications due to its characteristics of real-time, high efficiency and no radiation [1], [2], [3], [4]. Compare to the single-element ultrasonic transducer, the frame rate and scanning accuracy can be improved in array transducer by changing the scanning mode from mechanical to electrical means [5]. Consequently, the array transducer is more suitable for the medical ultrasonic diagnosis because of the advantages of real-time blood flow measurement, high frame rate and capability of dynamic focusing [6], [7].

Generally, the electromechanical properties of the piezoelectric materials, which is the core component of the array ultrasonic transducer, dominate the electroacoustic properties of the ultrasonic transducer such as bandwidth and relative sensitivity [8]. Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PMN-PT) single crystal has become the representative material for array ultrasonic transducer duo to its excellent piezoelectric coefficient and energy conversion efficiency compared to traditional piezoelectric ceramics, which can modify the electroacoustic performance of the array transducer and improve the quality of the ultrasonic imaging [9], [10], [11], [12], [13], [14].

Recently, the phenomenon that the dielectric and piezoelectric performance of PMN-PT single crystal can be enhanced obviously by using the alternating current poling (ACP) method has been widely reported by researchers [15], [16], [17], [18], [19], [20]. Yamashita et al. [21] reported that the ACP method can improve the piezoelectric properties of PMN-PT single-crystal firstly, which is more than 30% compared to direct current poling (DCP) samples. Yi Chang et al. [22] suggested that the piezoelectric coefficient and dielectric coefficient of ACP samples were improved by more than 21% compared to the traditional DCP method for PMN-0.30PT single crystal. The large electro-optical coefficient, ultrahigh piezoelectric coefficient and excellent electromechanical coupling factor of PMN-PT single crystal were simultaneously generated by using the ACP process and the results have been reported in Nature by Chaorui Qiu et al. [15]. At present, the researches of PMN-PT single crystal by using the ACP method focus on the improvement of material properties and the analysis of the enhancement mechanism. However, the application of PMN-PT single crystal by using ACP in phased array ultrasonic transducer is rarely reported. The influence of ACP single crystal on the electroacoustic performance of the phased array transducer should be evaluated in detail. Thus, it is significant to investigate and compare the electroacoustic properties of phased array transducer with ACP and DCP single crystal.

Finite element modeling (FEM) simulation has the feature of more comprehensive and accurate compared with the traditional KLM circuit model to simulate the electroacoustic properties of array transducer [23], [24], [25], [26]. Based on the FEM method, the effects of different materials on the properties of the array transducer can be predicted and obtained quickly and accurately. In this work, the FEM simulation and comparison of electroacoustic properties for ACP phased arrays and DCP phased arrays were investigated. The simulation results including the electrical impedance, vibration modal analysis, crosstalk level, pulse-echo response and beam profile of the ACP and DCP phased arrays.

Section snippets

Parameters of acoustic materials

The veracity of the parameters of acoustic material can affect the accuracy of the FEM simulation results. In this work, the specific parameters of the [0 0 1]-oriented PMN-0.25PT single crystal by ACP and DCP method were summarized in Table 1. It is significant to obtain the complete set of the dielectric, piezoelectric and elastic properties of the active materials because these data can be used to calculate the parameters of the passive material and design the structure of the phased arrays.

Electrical impedance of the single crystal

Fig. 4 shows the electrical impedance of ACP and DCP PMN-PT single crystal (height-extensional or beam mode) and the simulation results are summarized in Table 2. The value of f_a for ACP single crystal is almost the same as that of DCP single crystal while the f_r of ACP crystal is much lower than that of DCP crystal, resulting in the higher k^’₃₃ (0.888) of ACP single-crystal compared to that of the DCP crystal (0.847).

From the perspective of material properties, not only the piezoelectric

Conclusion

To sum up, the FEM simulation and comparison of electroacoustic properties for ACP phased arrays and DCP phased arrays were investigated. The simulation of electrical impedance for phased arrays reveals that the effective working bandwidth of ACP phased arrays is wider than that of DCP phased arrays as a whole. Besides, the ACP phased arrays have a higher k_eff compared to DCP arrays, which indicates that higher electromechanical conversion capacity is obtained to improve the bandwidth and

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.

Acknowledgments

This work was financially supported by the national key research and development Program of China (No. 2016YFC0301803 and 2016YFC0201102), the national natural science foundation of China (No. 61634007, 11827808 and 51831010), and the key program of Fujian institute of Innovation (No. FJCXY18040205).

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View full text

FEM simulation and comparison of PMN-PT single crystals based phased array ultrasonic transducer by alternating current poling and direct current poling

Highlights

Abstract

Introduction

Section snippets

Parameters of acoustic materials

Electrical impedance of the single crystal

Conclusion

Declaration of Competing Interest

Acknowledgments

Comput. Med. Imaging Graph.

Prog. Mater. Sci.

Ultrasonics

Prog. Mater. Sci.

Sens. Actuat. A: Phys.

Sens. Actuat. A: Phys.

Sens. Actuat. A: Phys.

Sens. Actuat. A: Phys.

Sens. Actuat. A: Phys.

A 100-MHz ultrasound imaging system for dermatologic and ophthalmologic diagnostics

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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

Sensor

Development of a 20-MHz Wide-Bandwidth PMN-PT Single Crystal Phased-Array Ultrasound Transducer

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A high frequency, high frame rate duplex ultrasound linear array imaging system for small animal imaging

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Piezoelectric single crystals of Pb(Mg1/3Nb2/3)O3-PbTiO3 and their applications in medical ultrasonic transducers

Proc. Int. Conf. Biomed. Eng. Inform.

Piezoelectric single crystals of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ and their applications in medical ultrasonic transducers