SYNTHESIS AND ELECTRICAL CHARACTERIZATION OF DOPED BETA-ALUMINA COMPOUNDS
Abstract
A series of first row transition metal doped (beta) and stabilized (beta)''-alumina compounds have been prepared to study the role of the dopant ion on the structure and stability of the beta-aluminas, as well as its effect on the resultant materials ionic conductivity. The majority of these compounds were synthesized by a skull melting technique, in which crystals are grown by slow cooling the melt from -2000(DEGREES)C. It was found that only cobalt, nickel, and zinc formed doped beta-alumina compounds. However, the resultant boules of these materials were a heterogeneous mixture of both the doped (beta) and stabilized (beta)'' phases. Characterization of these compounds with respect to their composition, structure, and distribution of the dopant ions was also performed. Electrical characterization, in the form of ionic conductivity measurements, were made via A.C. bridge/complex plane analysis, and phase synchronous detection/computer modeling methods. From these measurements it was found that the doped (beta)-alumina compounds had a consistently higher conductivity than comparable undoped materials, although still not quite as high as their stabilized (beta)''-alumina counterparts. The doped (beta) samples displayed a curvature in their (sigma)T vs 1/T plots, indicating a temperature dependent activation energy.
Degree
Ph.D.
Subject Area
Materials science
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