Research Projects

       The Iowa State University GOM group is part of a Materials World Network research project to study the Mixed Glass Former Effect. In collaboration with five other universities; Central Michigan University, Cornell University, Ilmenau (Germany), Münster (Germany), and Chalmers (Sweden). Between the six universities they will investigate the MGFE through IR and Raman Spectroscopy, NMR Spectroscopy, neutron diffraction, x-ray diffraction, modeling (simulation molecular dynamics and reverse Monte Carlo), and finally dielectric spectrometry. The purpose of this research collaboration is to develop a composition-property-structure-dynamics understanding of the MGFE which may lead to the development of new glassy electroltyes to solve the problems of polymer electrolytes.

Collaborator Log On: Gom MediaWiki

Lithium thiogermanate thin amorphous films are prepared as electrolytes forlithium rechargeable batteries by RF magnetron sputtering deposition in Ar and N₂ gases. The targets for RF sputtering are prepared by milling the appropriate amounts ofthe starting materials in the xLi₂S+GeS₂(x=2, 3), Li₄GeS₄ and Li₆GeS₅, binary system. The ~1 μm thin film electrolytes are grown onto a variety of substrates using 30 to 40 Watt power and 30 mtorr gas pressure. Films are sputtered in both inactive (Ar) andactive (N₂) gas atmospheres to examine the differences created between undoped anddoped (N) films. XPS and Auger spectroscopies are used to characterize thecomposition of the films. IR and Raman spectroscopy are used to further characterizethe chemical bonding in the films. Ionic conductivity measurements of the electrolytefilm using impedance spectroscopy are used to examine the Li₂S and N dependence ofthe conductivity.

       The secondary glass transition project dealt with using low temperature DSC techniques to confirm Oguni’s observations of a β-glass transition, which he found using adiabatic calorimetry.  The thermal properties of the Li₂O X + P₂O₅ (1-X) system were explored and the low temperature β–glass transition was not found.  Even though this secondary transition wasn’t discovered, the heat capacities of the mixed alkali system [(Na₂O + Li₂O) X + P₂O₅ (1-X)] can be reported. 

Magnesium ion conduction in non-oxide glasses

             In order to meet increasing energy storage demands, next generation batteries need to be produced.  An alternative to lithium-ion batteries is a solid-state magnesium battery.  Advantages to using magnesium over lithium are that magnesium is more environmentally friendly, cheaper, and has more charge carriers.  Kushwaha and Mishra have reported ionic conductivities as high as 10^-3 S/cm in bulk MgS-SiS2 glass-polymer composites.  Nevertheless, little structural characterization of these materials was reported or discussed.  The hypothesis under study is that by decreasing the charge density on the charge compensating anion of the host amorphous network, the binding energy between Mg2+ and S2- can be sufficiently reduced to produce measurable Mg2+ cation conduction.  In an effort to understand the high ionic conductivities in these bulk glasses, a selenide glass system has been studied.  Data collected using X-ray Diffraction, Differential Scanning Calorimetry, Infrared Spectroscopy, and Raman Spectroscopy has been taken and measurements of ionic conductivity using Impedance Spectroscopy are in progress.  Future research attempts to increase conductivity by exploring different glass modifiers in ternary glass systems and investigating structural features of the glasses.