Last Updated on May 9, 2023 by You Ling
In recent years, 1-3 piezoelectric composite materials have gained widespread attention as a unique class of functional materials. These composites exhibit a combination of desirable properties from both piezoelectric ceramics and polymer phases, offering significant advantages over conventional piezoelectric ceramics. The parallel arrangement of one-dimensional interconnected piezoelectric ceramic phase within a three-dimensional interconnected polymer matrix results in enhanced electromechanical conversion efficiency, lower acoustic impedance, and wider bandwidth, making them highly suitable for various applications.
Areas such as underwater acoustics, photoacoustic imaging, optoacoustic imaging, and biomedical engineering have greatly benefited from the development and application of 1-3 piezoelectric composites. Despite the challenges associated with fabrication complexity, cost, and working temperature range, ongoing research efforts are dedicated to optimizing the properties and expanding the applications of these composite materials. This introduction provides an overview of 1-3 piezoelectric composite materials, highlighting their advantages, drawbacks, and potential applications in various fields.
1、What is 1-3 Piezoelectric Composite Material
1-3 piezoelectric composite materials are composed of one-dimensional interconnected piezoelectric ceramic phases arranged parallel to a three-dimensional interconnected polymer phase. The addition of polymer effectively reduces the weakness of ceramics in strength and brittleness, reduces the lateral coupling of ceramics, and increases the longitudinal electromechanical conversion efficiency of the composite material. The material has low acoustic impedance, making it easy to match impedance with media such as water and skin. It also has a low dielectric constant, small static capacitance, high receiving voltage sensitivity, and high hydrostatic piezoelectric constant (gh=dh/ε), making it suitable for manufacturing hydrophones. The material’s low equivalent noise pressure level and high sensitivity are additional benefits. Due to the large attenuation of the polymer, the composite material has a low Qm value and is suitable for making broadband narrow pulse transducers, making it a widely used piezoelectric composite material.
2、1-3 Types of Piezoelectric Composite Materials
1-3 composites using the commonly used Dice&Fill method.
1-3 Dice & Fill Composites
1-3 Random Fiber Composites
1-3 Regular Fiber Composites
3、Advantages of 1-3 Piezoelectric Composite Materials
The advantages of piezoelectric composite materials over ordinary piezoelectric ceramics typically include:
(1) Weak lateral vibrations, resulting in low crosstalk sound pressure;
(2) Low mechanical quality factor Q;
(3) Large bandwidth (80%-100%);
(4) High electromechanical coupling coefficient;
(5) High sensitivity, with a better signal-to-noise ratio than standard PZT probes;
(6) Stable characteristics over a wide temperature range;
(7) Ability to process complex probe shapes using simple cutting and filling techniques;
(8) Ease of changing parameters such as sound velocity, acoustic impedance, relative permittivity, and electromechanical coefficients (as these parameters are related to the volume ratio of ceramic material);
(9) Ease of matching with materials of different acoustic impedances (from water to steel);
(10) Ability to adjust ultrasonic sensitivity through changes in the ceramic volume ratio.
4、Disadvantages of 1-3 Piezoelectric Composite Materials
Compared to ordinary piezoelectric ceramic components, the disadvantages of piezoelectric composite materials typically include higher costs and limited working temperature ranges. The fabrication process of piezoelectric composite materials is relatively complex, and the differences in volume fractions and structures of the two-phase materials for different application fields can lead to performance variations. Therefore, it is necessary to find the optimal material parameter values for each field to achieve optimal material performance. Furthermore, the materials can easily deform under external forces or heating, which can severely affect the associated acoustic radiation characteristics. At the same time, the presence of non-conductive polymers in the structure makes it challenging to draw out electrodes, which also restricts its application.
5、Typical Applications of 1-3 Piezoelectric Composite Materials
1-3 piezoelectric composite materials have excellent applications in underwater acoustic transducers. To further improve material performance, the cutting and filling method is used to produce composite materials. The impact of ceramic phase volume fraction on hydrostatic piezoelectric constant, hydrostatic sensitivity, electromechanical coupling coefficient, mechanical quality factor, and characteristic impedance is determined. The impact of the piezoelectric phase volume fraction and the width-to-height ratio of piezoelectric columns on performance is also studied. Experimental results show that the hydrostatic piezoelectric strain constant has its maximum value when the ceramic phase volume fraction is between 40% and 60%. The smaller the width-to-thickness ratio of the ceramic column, the thinner the ceramic column, and the higher the sensitivity of the underwater acoustic transducer. By reducing the side length of the piezoelectric phase or increasing the width of the grooves between the ceramic columns, the piezoelectric phase volume fraction can be reduced, making 1-3 piezoelectric composite materials more suitable for underwater acoustic transducers.
In recent years, 1-3 composite materials have also emerged in photoacoustic imaging and optoacoustic imaging. Li Yan et al. developed a miniature endoscopic probe for a 1-3 composite ultrasonic transducer based on PMN-PT/epoxy resin, improving material performance in terms of composite properties and applying it to dual-mode photoacoustic (PA)/ultrasound imaging systems (US). Compared to PMN-PT and lead zirconate titanate (PZT) composite ultrasonic transducers, the new ultrasonic transducer has improved bandwidth, PA image, and US image signal-to-noise ratio. The transducer features a high piezoelectric coefficient d33, high coupling coefficient Kt, and low dielectric loss, further enhancing the sensitivity of traditional PA/US imaging systems. From the perspective of material properties, temperature has a significant impact on the material. Researchers have studied the temperature characteristics of 1-3 piezoelectric composite materials and found that for materials made of PZT-5a/epoxy resin, the constants, piezoelectric constants, and electromechanical coupling coefficients increase with temperature in the range of 20°C to 120°C. Elastic stiffness coefficients and resonance frequencies decrease with increasing temperature, while dielectric losses show a pattern of first increasing, then decreasing, and finally increasing again as the temperature rises. When the piezoelectric phase material is changed to PZT-PZM-PZN, the dielectric loss increases with increasing temperature. Overall, the conclusions on dielectric constants and electromechanical coupling coefficients may be consistent at different times, while the impact on dielectric loss may vary. These findings can help expand the application of 1-3 composite materials in high-temperature transducers. Not only do changes in the piezoelectric phase affect material properties, but differences in performance due to changes in the polymer phase have also attracted attention from researchers. Due to the presence of the polymer phase, the low mechanical quality factor makes it challenging for 1-3 piezoelectric composite materials to be used in high-power ultrasonic transducers. Research has shown that selecting low-loss, low-modulus polymers can improve the electromechanical coupling and mechanical quality factor of 1-3 piezoelectric composite materials, allowing 1-3 composite materials to be successfully applied in high-power ultrasonic transducers.
In the field of biomedical engineering, ultrasonic transducers have become a research hotspot in ultrasound medical diagnosis. Researchers have developed 1-3 piezoelectric composite material shell-focused transducers, which improve bandwidth, electromechanical conversion rate, and lower impedance compared to ordinary ceramic transducers, playing a vital role in enhancing the performance of high-intensity focused medical equipment. Other researchers have applied 1-3 piezoelectric composite materials to intravascular ultrasound imaging. Due to the small size of blood vessels, intravascular ultrasound imaging usually has a lower lateral resolution. Focused transducers made from PZT/epoxy resin 1-3 piezoelectric composite materials effectively overcome this limitation, demonstrating that 1-3 piezoelectric composite material transducers have a bright future in the field of biomedical engineering.
6、Conclusion
1-3 piezoelectric composite materials have shown remarkable potential in a wide range of applications, such as underwater acoustics, photoacoustic imaging, optoacoustic imaging, and biomedical engineering. By combining the favorable properties of piezoelectric ceramics and polymer phases, these composites offer significant advantages over conventional piezoelectric ceramics, including improved electromechanical conversion efficiency, lower acoustic impedance, and wider bandwidth. Although there are challenges related to fabrication complexity, cost, and working temperature range, ongoing research is continually seeking to optimize the properties and expand the applications of these composite materials. As our understanding of 1-3 piezoelectric composites deepens, it is anticipated that their use will continue to grow and contribute to further advancements in various fields.
