Lead-free Radio-pure Textured Piezoelectric Ceramics for Acoustic Sensors in Dark Matter Search

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NON-TECHNICAL DESCRIPTION: Currently most of the piezoelectric ceramic materials utilized for actuator and transducer applications contain high concentrations of lead, which is toxic for both humans and environment. If the products containing lead are not properly discarded or recycled, then there is high possibility for lead entering the soil and water streams. Further, there is health-risk posed for humans handling the lead-based materials during manufacturing and deployment. Thus, environmental regulations in many parts of the world are requiring the elimination of lead from all consumer items. In applications such as acoustic detectors, there is essential need to find lead-free piezoelectric alternatives to achieve desired sensitivity. However, electrical properties of all the known lead-free piezoelectric materials remains lower than those lead-based materials. In this project, lead-free piezoelectric ceramics are being studied to discover composition and microstructure with enhanced piezoelectric response. Outcomes from this research stand to strengthen the US piezoelectric ceramic industry leadership. Lead-free material formulations and specialized ceramic manufacturing methodology are being provided to the US piezoelectric manufacturers. Undergraduate and graduate students, high school science teachers and postdoctoral researchers are being professionally trained in this project to develop understanding of ceramic industry and piezoelectric applications. NSF I-Corps program is leveraged to support the training of students to become drivers of research commercialization. Furthermore, students are being exposed to methods for transition of university-based technologies through partnership with Ben Franklin Technology Partner’s TechCelerator.TECHNICAL DETAILS: In this project, (K,Na)NbO3 based high piezoelectric constant – high Curie temperature lead-free piezoelectric material is being designed, synthesized and characterized. Template grain growth process is used to synthesize ceramics with specific crystallographic grain orientation. Using the grain-oriented materials, extensive investigations are being conducted to understand how phase transitions, domain structures, and local crystal structures influence the piezoelectric response. Furthermore, the research focus is being placed on understanding the influence of relaxor state on piezoelectric performance. Phase field model is being used to investigate the role of local structural heterogeneity on electromechanical parameters. Self-polarization due to grain orientation along the spontaneous polarization direction is being quantified to reveal its contribution in achieving large piezoelectric response in an engineered material. Synthesized textured piezoelectric elements with requisite electromechanical behavior is incorporated into acoustic transducers, subjected to the extreme environmental conditions of the bubble chamber and tested for performance in small environmental test vessels. Knowledge generated from the project on lead-free material design and manufacturing is being provided to US companies to expedite their progress in finding lead-free alternatives and thereby developing next generation of applications such as medical imaging, ultrasonic home appliances, acoustic detectors and precision positioning systems. Undergraduate and graduate students are being trained in cross-cutting multidisciplinary disciplines of piezoelectric ceramics, ceramic processing science, multiscale characterization, acoustics, and physics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.