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

非技术描述：目前大多数用于执行器和换能器的压电陶瓷材料都含有高浓度的铅，这对人类和环境都是有毒的。如果含铅产品没有被适当地丢弃或回收，那么铅很有可能进入土壤和水流。此外，在制造和部署过程中，处理含铅材料的人会面临健康风险。因此，世界上许多地方的环境法规都要求从所有消费品中消除铅。在声学探测器等应用中，有必要找到无铅压电替代材料来实现所需的灵敏度。然而，所有已知的无铅压电材料的电学性能仍然低于铅基材料。在这个项目中，我们正在研究无铅压电陶瓷，以发现具有增强压电响应的成分和微观结构。这项研究的成果将加强美国压电陶瓷行业的领导地位。无铅材料配方和专业陶瓷制造方法正在提供给美国压电制造商。本科和研究生、高中理科教师和博士后研究人员在该项目中接受专业培训，以发展对陶瓷工业和压电应用的理解。NSF I-Corps项目旨在支持学生的培训，使其成为研究商业化的驱动力。此外，通过与Ben Franklin技术合作伙伴的TechCelerator合作，学生们将接触到以大学为基础的技术转型方法。本项目设计、合成并表征了基于（K,Na）NbO3的高压电恒高居里温度无铅压电材料。采用模板晶粒生长法合成具有特定晶粒取向的陶瓷。利用晶粒取向材料，人们正在进行广泛的研究，以了解相变、畴结构和局部晶体结构如何影响压电响应。此外，研究的重点是了解弛豫状态对压电性能的影响。采用相场模型研究了局部结构非均质性对机电参数的影响。由于晶粒取向沿自发极化方向的自极化被量化，以揭示其在实现工程材料的大压电响应中的贡献。将具有必要机电性能的合成纹理压电元件集成到声学换能器中，在气泡室的极端环境条件下进行测试，并在小型环境试验容器中进行性能测试。该项目所产生的无铅材料设计和制造方面的知识正在提供给美国公司，以加快他们在寻找无铅替代品方面的进展，从而开发下一代应用，如医疗成像、超声波家用电器、声学探测器和精确定位系统。本科生和研究生主要从事压电陶瓷、陶瓷加工科学、多尺度表征、声学和物理学等交叉学科的培养。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.