Ternary and Quaternary Nitrides

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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.