Ternary and Quaternary Nitrides

本项目的目的是探索三元和四元氮化物的制备，并确定其性质。在氧化物化学中，三元和季元化合物提供了比二元化合物更大、更可调、在性质上不同、更有用的一组性质，因此，由于已知了这么多有用的二元氮化物，三元和季元氮化物最终也会提供同样的性质。虽然已经发现了结构上有趣的化合物，其中一些具有不寻常的性质，但对这种三元和季氮化物的研究仍处于起步阶段，特别是与三元和季氧化物，甚至与硫化物，磷化物，碳化物等相比。新的合成技术正在被发明和开发，以制备各种各样的新型氮化物。虽然在美国只有少数几个小组在探索氮化物的固态化学，但在欧洲和日本，这是一个非常活跃的研究领域。与其中许多团体的密切联系以及美国的努力促成了交换学生和博士后的项目。该项目将侧重于使用熔融金属及其合金作为助熔剂（溶剂）来制备导电的，甚至可能是超导的，以及磁性多元氮化物，将研究其潜在的技术用途和新现象。低熔点金属，如钠、锌、镓、铟、锡和铋，将为此目的进行探索。初步结果表明，这些助熔剂和这些助熔剂的合金将在生产大量具有新结构和新性能的新化合物方面发挥重要作用。这项研究也将成为培养固态化学科学和艺术方面的本科生、研究生和博士后的工具。这项研究的结果将通过WEB、出版物、研讨会、专业会议，并酌情通过专利广泛传播。根据目前的研究结果，与工业界的互动正在进行中。这些方法和结果已经并将继续被纳入本科课程，特别是由PI开发的固态化学研究生课程。PI和他的研究小组也非常积极地将科学带给广泛的受众，包括K - 12学校的孩子，初中和高中的科学教师以及社区大学，以及小型学院和大学的本科生。后者的学生没有机会参与材料化学前沿的研究或使用康奈尔大学提供的先进仪器。K - 12学生通过在当地学校进行的化学演示来学习。来自小型学院的本科生和当地高中教师在夏季花长达10周的时间在这些实验室工作。PI为《问科学家》周刊撰写的几个地方报纸专栏覆盖了整个社区，这些专栏有8万名读者。这些外联活动不仅旨在吸引广泛的年轻人了解科学，而且也许更重要的是，它们是帮助培养具有科学素养的公众的一个组成部分。二元氮化物已经有许多重要的用途。这些包括氮化铝（高导热基板），氮化硅（作为电子产品上的化学气相沉积涂层等），氮化钛（工具硬涂层），氮化钽（电子产品中的金属导体和扩散屏障，珠宝中的彩色表面，艺术显示器等），氮化铌（薄膜超导器件），氮化镓（蓝色发光二极管，高速-高功率电子产品）。预计三元和四元氮化物将最终为推动新技术的发展提供一类全新的高价值功能材料。在这些领域受过训练的学生在学术、工业和政府实验室部门的广泛工作中非常有竞争力。

The goal of this project is to explore the preparation of ternary and quaternary nitrides and determine their properties. As with oxide chemistry where ternaries and quaternaries offer a greater, more tunable, qualitatively different and more useful set of properties than the binaries, so too is it expected that ternary and quaternary nitrides will eventually provide the same since so many useful binary nitrides are known. Although structurally interesting compounds have been found, some with unusual properties, the study of such ternary and quaternary nitrides is still in its infancy, especially when compared to ternary and quaternary oxides, or even to sulfides, phosphides, carbides, etc. New synthetic techniques are being invented and exploited to prepare a wide variety of novel nitride compounds. Although there are only a few groups in the U.S. exploring the solid state chemistry of nitrides, it is a very active field of research in Europe and Japan. Close ties to many of those groups and this U.S. effort have resulted in programs for exchanging students and postdocs. This project will focus on the use of molten metals and their alloys as fluxes (solvents) to prepare conducting, possibly even superconducting, as well as magnetic multinary nitrides that will be examined for potential technological uses and for novel phenomena. Low melting point metals, such as sodium, zinc, gallium, indium, tin, and bismuth will be explored for this purpose. Initial results suggest that these fluxes and alloys of these fluxes will be highly useful for producing a large number of new compounds with novel structures and properties. This research will also be a vehicle for the training of undergraduates, graduate students and postdocs in the science and art of Solid State Chemistry. The results of this research will be widely disseminated via the WEB, publications, seminars, professional meetings and, where appropriate, via patents. Interactions with industry prompted by current findings are underway. The methodology and results have also been and will continue to be incorporated in undergraduate courses and especially in a graduate course on Solid State Chemistry developed by the PI. The PI and his research group are also very active in bringing science to a wide audience, including K - 12 school children, science teachers in middle and high schools as well as community colleges, and to undergraduates from smaller colleges and universities. The latter students do not otherwise have the opportunity to be involved in research at the forefront of materials chemistry or use the advanced instrumentation available at Cornell University. K - 12 students are reached through Chemistry Demonstrations that are performed in the local schools. Undergraduate students from smaller colleges and local high school teachers spend up to 10 weeks in the summer working in these laboratories. The entire community is reached by several local newspaper columns the PI has written for the Ask a Scientist weekly feature reaching 80,000 readers. These outreach activities are not only aimed at attracting a broad cross section of young people to science, but perhaps more importantly, they are an integral part of helping to develop a scientifically literate public. %%%There are already many important uses of binary nitrides. These include aluminum nitride (high thermal conductivity substrates), silicon nitride (as chemical vapor deposited coating on electronics, etc.), titanium nitride (hard coatings for tools), tantalum nitride (metallic conductors and diffusion barriers in electronics, colored surfaces in jewelry, artistic displays, etc.), niobium nitride (thin film super-conducting devices), gallium nitride (blue light emitting diodes, high speed - high power electronics). Is it expected that ternary and quaternary nitrides will eventually provide a whole new class of functional materials of high value to advancing new technologies. Students trained in these areas are very competitive for a wide range of jobs in the academic, industrial, and government laboratory sectors.