3 research outputs found
Solution based processing of garnet type oxides for optimized lithium-ion transport
Current lithium based portable electrochemical storage devices are limited by the inherent instability and volatility of conventional electrolytes materials. Ceramic materials show much promise for use in advanced lithium based battery systems due to their inhibition of dendritic growth and high thermal and chemical stability. The main drawback of solid materials is their low ionic conductivity, relying on lattice hopping to transport ions between electrodes during cycling. Garnet type oxides, specifically of the base compositions Li7La3Zr2O12 and Li5L a3Bi2O12 have been synthesized through Pechini method solution based processing by the dissolution of reagent salts into nitric acid and creation of a chelated polymerized complex. Through an extensive examination of the subsequent processing conditions, it is revealed that the many contributing factors in this process can be optimized to create mixtures of these two structures. By changing the composition, the structure-property relationships between Li7-xLa3Zr2-xB ixO12 compounds are examined demonstrating that stoichiometric variations offer improvements to both the degree of sintering and the ionic transport in this promising class of materials
Proton Doping and Characterization of Rare Earth Nickelates
Perovskite rare earth nickelates with formula RNiO3 (R = trivalent rare earth element) feature exceptional electrical behavior and performance in a wide variety of functional applications due to their unique metal-insulator transition. This distinctive phase transition is caused by charge disproportionation as the crystal structure distorts upon temperature change and electron-electron interactions result in a modified band structure. However, electron doping of the same nickelate systems has created a more pronounced phase transition wherein unprecedented resistivity changes on the order of 1010 Ω*cm are achieved through the opening of a wide bandgap. In this work, a new method for inducing a water-mediated electrically driven phase transition is examined through the use of various processing methods and investigation of subsequent effects on the structural and material properties. Electrochemically driven doping of protons is caused through potentiostatic bias applications and linear sweep voltammetry, while the effects on the electrical and optic properties are observed and correlated with structural data collected through x-ray and neutron scattering. Finally, the effects of A-site substitution (Sm, Nd, Eu) on the doping process are assessed