Flux Syntheis and Properties of New Crystalline and Glassy Chalcogenides

Michigan State University, East Lansing MI

Investigators

Abstract

The goal of this project is to synthesize and characterize new solid-state materials in the metal thiophosphate and selenophosphate families. The metal thiophosphate and selenophosphates show a very rich chemistry that is based on anions that form in chalcophosphate fluxes by simple in-situ fusion, and these act as fundamental structural building blocks. Areas to be explored include alkali metal-free ternary metal-and rare-earth-metal- thiophosphates and selenophosphates, corresponding alkali metal quaternary derivatives and also glasses formed from the manipulation of these materials. Thioarsenate and selenoarsenate fluxes will also be explored to discover corresponding arsenic compounds. Characterization of the new materials will include structural determinations by single-crystal X-ray scattering methods and the measurement of physical properties such as optical absorption, thermal behavior and electrical conductivity. The structure of glasses will be probed with pair distribution function (PDF) analysis. The molten alkali poly-thiophosphate and poly-selenophosphate salts, which are the reactive solvents in this project, will be studied by Nuclear Magnetic Resonance spectroscopy in order to understand the identity, distribution, and chemistry of the anions that form in chalcophosphate fluxes. Eventually we wish to control the stabilization and incorporation of specified building blocks in synthetic target compounds. The ultimate goal of this research project is to enhance our knowledge of the chemistry of chalcogenides and render the chemistry more controllable and predictable so useful new materials can be designed. This project has a very strong education component that aims to educate students in the advanced subject of solid state synthesis including non-oxide materials discovery and novel state-of the-art laboratory techniques. The discovery of new classes of solid state materials with novel composition and structure, as well as an understanding of their chemical behavior and physical properties such as optical and electronic behavior are important to industry. For example, the glass versions of the metal-thiophosphate and -selenophosphates show controllable amorphous to crystal phase changes and may have potential for memory storage applications. Students trained in these areas are well poised to exploit current and future academic and industrial job opportunities.