Mixed electronic and ionic conduction in beta alumina type compounds
Abstract
Mixed conduction is a phenomenon of exhibiting both ionic and electronic conduction. $\beta$-alumina type compounds ($\beta$-alumina, $\beta\sp{\prime\prime}$-alumina and their derivatives) have been known to exhibit very high (sodium) ionic conductivity. If the electronic conductivity in these materials can be enhanced considerably, then such materials would be the ideal choice as electrodes in many applications. The conditions under which the electronic conductivity in $\beta$-alumina type compounds can be induced are explored. Examination of the mechanism of the electronic conduction in $\beta$-alumina type compounds has led to the conclusion that addition of mixed valent ions of the same type (such as Ti$\sp{3+}$ and Ti$\sp{4+}$) beyond a certain amount (percolation threshold) in the octahedral sublattice is necessary to enhance the electronic conductivity in these compounds. The charge compensation that is connected with doping these materials with different ions is also discussed. The experimental results of the synthesis and characterization of Ti along with Ni doped $\beta$-alumina are presented. The site preference and the valence state of Ti in $\beta$-alumina are determined by UV/Visible Spectroscopy and Electron Energy Loss Spectroscopy (EELS) respectively. A new method of determining the valence state of Ti and Fe in ceramic compounds using EELS is also discussed.
Degree
Ph.D.
Advisors
Sato, Purdue University.
Subject Area
Materials science
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