CAS: Design and discovery of lead-free hybrid layered perovskite dielectrics

非技术摘要：电介质材料在现代社会中得到广泛应用。铁电体用于制造电容器、天线和滤波器等电路元件;压电体用于声纳和超声成像技术;热电体用于红外成像设备等应用。绝大多数介电材料是无机氧化物，其中许多含有铅。在材料研究部门的固态和材料化学计划以及电子和光子材料计划的支持下，主要研究人员和他的团队在新兴的混合层状钙钛矿家族中发现和开发新的介电材料，这些材料由带正电的有机阳离子和带负电的交替层组成，角连接金属卤化物八面体。通过合成和表征的迭代程序，研究了这些材料的复杂晶体化学的规则。然后，新的知识被用于设计新的电介质和磁性材料，这些材料可以作为当今广泛使用的铅基氧化物的替代品。此外，真实的课堂研究实验在俄亥俄州州立大学的普通化学课程中开发和实施，每年影响数百名学生，在他们的大学教育的早期阶段向他们介绍研究和关键材料化学概念。最后，本项目支持的研究生和本科生获得培训，为他们在学术界和工业界的成功职业生涯做好准备。技术摘要：该研究由材料研究部的固态和材料化学计划以及电子和光子材料计划支持，可分为两个主要领域。第一个推力涉及合成和表征的层状双钙钛矿，含有棋盘图案的1+和3+阳离子的无机层的八面体网站。当与适当的有机阳离子配对时，这些材料能够模拟最近在铅基混合层状钙钛矿中看到的有前途的介电性质，同时避免掺入有毒元素，如铅和镉。 相变的研究，以了解这些材料中的结构指导力，并揭示各种变形机制相互耦合的机制。第二个推力为含有磁性阳离子的化合物带来了类似的方法，如Cu 2+，Mn 2+和Fe 2+。该研究利用有机层和无机层之间的相互作用来放大极性晶体中的电极化，并增强磁性和铁电序参数之间的耦合。该研究计划的首要主题是了解这些混合材料的复杂晶体化学，并利用这些知识设计和开发新的铁电体，反铁电体，压电体，多铁性，铁电半导体，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识产权进行评估来支持。优点和更广泛的影响审查标准。

Non-Technical Abstract:Dielectric materials find widespread application in modern society. Ferroelectrics are used to make circuit elements such capacitors, antennas and filters; piezoelectrics are used in sonar and ultrasound imaging technologies; pyroelectrics are used in infrared imaging devices among other applications. The vast majority of dielectric materials are inorganic oxides, many of which contain lead. With support from the Solid State and Materials Chemistry Program and the Electronic and Photonic Materials Program in the Division of Materials Research the principle investigator and his group discover and develop new dielectric materials within the emerging family of hybrid layered perovskites, materials that are made up of alternating layers of positively charged organic cations and negatively charged, corner-connected metal-halide octahedra. Through an iterative program of synthesis and characterization the rules governing the complex crystal chemistry of these materials are studied. The new knowledge is then used to design new dielectric and magnetic materials that can serve as alternatives to the lead-based oxide dielectrics that are widely used today. In addition, authentic in-class research experiments are developed and implemented in general chemistry courses at Ohio State University that impact hundreds of students per year, introducing them to research and key materials chemistry concepts at an early stage of their college education. Finally, the graduate and undergraduate students supported by this project gain training that prepares them for successful careers in academia and industry. Technical Abstract:The research, supported by the Solid State and Materials Chemistry Program and the Electronic and Photonic Materials Program in the Division of Materials Research, can be divided into two thrust areas. The first thrust involves synthesis and characterization of layered double perovskites that contain a checkerboard pattern of 1+ and 3+ cations on the octahedral sites of the inorganic layers. When paired with the appropriate organic cations these materials are able to mimic the promising dielectric properties that have recently been seen in lead-based hybrid layered perovskites, while avoiding incorporation of toxic elements such as lead and cadmium. Phase transitions are studied to understand the structure directing forces in these materials and reveal the mechanisms by which various distortion mechanisms couple to one another. The second thrust brings a similar approach to compounds that contain magnetic cations, like Cu2+, Mn2+ and Fe2+. The research leverages the interactions between organic and inorganic layers to amplify the electrical polarization seen in polar crystals and enhance the coupling between magnetic and ferroelectric order parameters. The overarching theme of the research program is to develop an understanding of the complex crystal chemistry of these hybrid materials and use that knowledge to design and develop new ferroelectrics, antiferroelectrics, piezoelectrics, multiferroics, ferroelectric semiconductors, and related classes of multifunctional dielectric materials.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.