CAREER: Ion-Transport in Beta-Gallia-Rutile Intergrowths: An Investigation of Structure-Property Relationships

Alfred University Ny State College Of Ceramics, Alfred NY

Investigators

Abstract

0093690 Edwards The overarching goal of this Faculty Early CAREER Development project is to integrate research on beta-gallia-rutile (BGR) intergrowths with undergraduate and graduate education and outreach. The goal of the research project is to develop a fundamental understanding of the ionic transport in beta-gallia-rutile intergrowths. Expressed as Ga4Mn-4O2n-2 (M = Ge, Ti, Sn, n>5), the BGR intergrowths possess one-dimensional tunnels, which are suitable "hosts" for small-to-medium sized "guest" cations. Because the BGR intergrowths form two homologous series in which the density and spatial arrangement of the tunnels can be controlled, the intergrowths provide a unique opportunity to systematically investigate ion transport in one-dimensional tunneled oxides. In this work, novel materials based on parent BGR intergrowth structures will be synthesized by incorporating univalent cations (Li+, Na+, K+,and Ag+) into the one-dimensional tunnels and by replacing host-structure cations with various M3+ and M4+ cations to tailor the size and arrangement of the tunnels and to facilitate ionic exchange (storage) and ion conduction. The work will define the phase stability of the intergrowths with respect to the univalent tunnel cations as well as the trivalent and tetravalent framework cations and will correlate structural features such as tunnel size, spatial arrangement, and chemistry to the resulting transport behavior. Both polycrystalline and single-crystal materials will be studied. Phase stability and structure will be determined by X-ray diffraction, neutron diffraction, and electron microscopy. The ionic transport behavior will be elucidated using electrochemical insertion techniques, AC impedance spectroscopy, and DC electrical measurements. Expected outcomes of the research are 1) an increased understanding of phase stability in complex oxide systems, 2) an improved understanding of ion transport in one-dimensional oxide systems, and 3) the development of new materials that may find applications as solid-electrolytes, reversible ion electrodes, ion separators, chemical sensors and catalysts. The educational component of the project involves engaging undergraduate and graduate students in challenging research projects, developing a laboratory course on electronic materials that incorporates team work activities and utilizes open-ended problems, and developing a demonstration module that can be incorporated into Alfred University's Summer Institute for Science and Engineering High School Juniors. %%% Ionic transport is an underlying phenomenon in many important devices including fuel cells for energy conversion, batteries for energy storage, and sensors for environmental monitoring. Ionic transport involves the movement of mobile cations within pathways that may be 1-dimensional tunnels, 2-dimensional layers or a 3-dimensional network of channels. Understanding the factors that affect cation transport through these pathways is critical to developing new and improved materials. The knowledge gained in the project will advance the fundamental understanding of ionic transport, which will ultimately result in improvements of existing devices and the development of new materials. In terms of educational benefits, the project will expose high-school students to opportunities in science and engineering and will engage future scientists and engineers in a challenging research project that will foster creativity and innovation.