Ternary and Quaternary Nitrides

本项目的目标是探索三元和四元氮化物的制备方法，并确定它们的性能。与氧化物化学一样，三元和四元氮化物提供了比二元化合物更大、更可调、质量不同和更有用的一组性质，因此也预计三元和四元氮化物最终将提供相同的性质，因为已知了如此多有用的二元氮化物。虽然已经发现了一些结构有趣的化合物，其中一些具有特殊的性质，但这类三元和四元氮化物的研究仍处于起步阶段，特别是与三元和四元氧化物相比，甚至与硫化物、磷化物、碳化物等相比。人们正在发明和开发新的合成技术来制备各种新型氮化物化合物。尽管美国只有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。与其中许多组织的密切联系以及美国的这一努力导致了交换学生和博士后的计划。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、甚至超导以及磁性多元氮化物，这些氮化物将被用于潜在的技术用途和新的现象。为此目的，将探索低熔点金属，如钠、锌、镓、铟、锡和铋。初步结果表明，这些助熔剂和这些助熔剂的合金将非常有助于生产大量具有新结构和性能的新化合物。这项研究还将成为培养本科生、研究生和博士后在固体化学科学和艺术方面的工具。这项研究的结果将通过网络、出版物、研讨会、专业会议以及适当的专利广泛传播。目前的研究结果推动了与行业的互动。这一方法和成果也已经并将继续纳入本科课程，特别是国际固体化学研究生院制定的固体化学研究生课程。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学校的儿童、初中和高中的科学教师以及社区大学的学生，以及来自较小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，也没有机会使用康奈尔大学提供的先进仪器。通过在当地学校进行的化学演示，可以接触到K-12学生。来自规模较小的大学的本科生和当地的高中教师在夏天花了长达10周的时间在这些实验室工作。整个社区都受到了当地报纸的几个专栏的影响，这些专栏是为《问科学家》周刊专栏撰写的，读者达到了8万人。这些外展活动的目的不仅是吸引广泛的年轻人接触科学，或许更重要的是，它们是帮助培养具有科学素养的公众的不可或缺的一部分。二元氮化物已经有许多重要的用途。这些包括氮化铝(高导热系数衬底)、氮化硅(作为化学气相沉积在电子产品上的涂层等)、氮化钛(工具上的硬质涂层)、氮化钽(电子产品中的金属导体和扩散障碍，在珠宝、艺术显示器等方面的有色表面)、氮化Nb(薄膜超导器件)、氮化镓(蓝色发光二极管、高速高功率电子设备)。预计三元和四元氮化物最终将提供一类全新的高价值功能材料，以推动新技术的发展。在这些领域接受培训的学生在学术、工业和政府实验室部门的广泛工作中具有很强的竞争力。

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.