SusChEM: Nanoscale Insight into Electric Fatigue of Lead-Free Piezoelectric Ceramics

非技术描述：铅干扰许多身体过程，包括神经系统的发育，因此对儿童特别有毒，并可能导致永久性学习和行为障碍。自1970年代以来，限制铅使用的法规，如强制回收汽车铅酸电池和禁止含铅汽油和含铅油漆，大大减少了发达国家的铅暴露。然而，铅是世界上生产最多的金属之一，仍然广泛用于各种产品。即使在今天，铅中毒仍然是最大的环境医学问题之一，就暴露的人数和公共卫生费用而言。在电子设备和医疗器械中，铅主要用于压电元件。这些元件将电信号转换为声学信号，对于水下通信和超声医学成像至关重要。为了进一步减少铅污染，为子孙后代创造一个可持续发展的环境，必须用无铅压电材料取代目前使用的含铅压电材料。这个基础研究项目旨在为数十亿美元的压电行业确定环境友好的成分。这一成果有可能极大地造福于人类健康和环境。技术特点：压电器件中的核心元件由锆钛酸铅陶瓷制成，其含量超过60重量%。中铅的铅的毒性引起了严重的环境问题，限制其使用的立法推动了世界范围内对无铅压电材料开发的广泛研究。在过去的十年中，在成分设计和加工控制方面取得了重大进展，现在正在促使研究界将这些科学成果转化为富有成效的环境安全产品。因此，与性能稳定性和设备可靠性相关的基本问题需要立即彻底解决。在真实的设备中，这些陶瓷几乎总是由循环的电力或机械力驱动，并且最终它们的性能由于疲劳而劣化。电疲劳退化是无铅压电陶瓷器件稳定性和可靠性的主要问题。在该项目中，爱荷华州的研究人员首次通过在透射电子显微镜内对无铅陶瓷试样进行电循环来研究电疲劳的微观结构机制。这种创新的原位研究可以识别导致快速疲劳退化的主要微观结构特征，因此，将有助于找到减轻性能退化的方法。无铅成分可以在广泛的工程和医疗技术中取代锆钛酸铅，这极大地有助于为儿童创造一个可持续的未来。该项目还旨在通过培训学生掌握尖端材料研究技术，对研究生和本科生教育产生广泛影响。此外，正在开发一个关于铅毒性的iPad应用程序，供高中生和本科生演示。

NON-TECHNICAL DESCRIPTION: Lead interferes with many body processes, including the development of the nervous system, and therefore is particularly toxic to children, and can cause permanent learning and behavior disorders. Regulations restricting lead use, such as enforced recycling of lead-acid batteries of automobiles and the ban of leaded gasoline and lead paint, have greatly reduced lead exposure in the developed world since the 1970s. However, lead is one of the most produced metals in the world and is still widely used in various products. Even today, lead poisoning remains one of the largest environmental medicine problems in terms of numbers of people exposed and the public health toll it takes. In electronic devices and medical instruments, lead is primarily used in piezoelectric elements. These elements convert electrical signals into acoustic signals and are critical for underwater communications and ultrasound medical imaging. To further reduce lead contamination and create a sustainable environment for future generations, currently used lead-containing piezoelectric materials must be replaced by lead-free ones. This project on fundamental research aims to identify environmentally-friendly compositions for the multi-billion dollar piezoelectrics industry. The outcome has the potential to greatly benefit both human health and the environment. TECHNICAL DETAILS: The core elements in piezoelectric devices are made of lead zirconate titanate ceramics, which contain more than 60 wt.% of lead. The toxicity of lead has raised serious environmental concerns and legislations on restriction of its use have driven extensive worldwide research on the development of lead-free piezoelectric materials. Significant progress has been made in the past decade in composition design and processing control and the research community is now being prompted to move these scientific achievements into fruitful environmentally safe products. As such, fundamental issues related to performance stability and device reliability need to be addressed thoroughly and immediately. In real devices during service, these ceramics are almost invariably driven by cyclic electric or mechanical forces, and eventually their performances deteriorate due to fatigue. Electric fatigue degradation is the major concern for stability and reliability of piezoelectric devices utilizing lead-free ceramics. In this project, the researchers at Iowa State are investigating the microstructural mechanisms of electric fatigue through electrically cycling lead-free ceramic specimens inside the transmission electron microscope for the first time. Such innovative in situ studies can identify the primary microstructural feature that leads to fast fatigue degradation and therefore, will help find ways to alleviate the property degradation. Lead-free compositions can then replace lead zirconate titanate in a wide range of engineering and medical technologies, which greatly help to create a sustainable future for children. This project is also designed to have a broad impact on graduate and undergraduate education by training students in cutting-edge materials research techniques. Furthermore, an App for iPads on the toxicity of lead is under development for demonstrations to high school students and undergraduate students.