Synthesis And Structure-Function Relationships In Ferecrystals: New Compounds Poised Between The Crystalline And Amorphous States

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

TECHNICAL SUMMARY: The synthesis of new inorganic compounds with designed extended structures is one of the grand challenges in materials research. This project, funded by the Solid State and Materials Chemistry Program, will use a newly developed synthetic strategy to prepare ferecrystals (from Latin fere, meaning almost), new materials that are poised between the crystalline and amorphous states. Ferecrystals have been shown to have unusual properties - the lowest thermal conductivity ever reported for a fully dense solid, charge density wave and other charge localization phenomena, and superconductivity. The focus of this effort is to examine the dependence of electrical properties and charge density wave transitions on nanostructure (n, m and different layer sequences with the same number of constituent layers in each unit cell) in [(MSe)1+d]m[TSe2]n compounds, which contain rock salt structured MSe constituents where M is Sn, Pb, Bi or a rare earth metal interleaved with transition metal diselenides, TSe2, where T is V, Nb, or Ta. n and m denote the number of layers of each constituent and d denotes the degree of misfit in the a-b plane between the components. It will be determined how properties and structure of the constituents change within a series of structural isomers, how changing the layer thickness from below to above the length scale of the charge depletion region affects stability, and how charge transfer affects carrier concentrations as the ratio of n to m is varied. NON-TECHNICAL SUMMARY: The designed synthesis of new compounds with targeted structure is one of the grand challenges in materials research and critical to both fundamentally understanding and exploiting structure-function relationships. This research uses a new synthesis technique developed in Oregon with NSF support to prepare several series of new structurally related compounds which will enable properties to be studied as a function of nanostructure in a manner that has not previously been possible and provide an improved understanding of structure-property relationships. The development of new synthetic techniques is a vital step necessary to advance fundamental science, critical to current and future technologies and crucial to international competitiveness. The graduate students in this research program obtain a broad technical background in deposition technologies and thin film characterization techniques, preparing them for future careers in high tech industries, academia or national laboratories. Internships provide an opportunity for graduate students to ?test drive? future careers and expand their knowledge base. Internships result in more productive graduate researchers, facilitates the transfer of knowledge to industry, and will increase the impact of the proposed project. Science pub events by the principle investigator in rural Oregon will focus on illustrating the connectivity between NSF-sponsored research, education and national competitiveness