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Title:Part One: Extensions of the E and C Equation. Part Two: Measurements of Dielectric Relaxation in Strontium Doped Lanthanum Orthoferrites Using Dielectric Time Domain Spectroscopy
Author(s):Doan, Peter Eric
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Physical
Abstract:Part One. The relationships between the Kamlet-Taft $\beta$-$\pi\sp\*$ solvation approach and the E and C equation are investigated. The breakup of solvation effects into nonspecific ($\pi\sp\*$) and specific Lewis base interactions ($\beta$) is found to be consistent with the E and C approach. The $\beta$ parameter is shown to be a special case of the E and C equation for acids with a C$\sb{\rm A}$/E$\sb{\rm A}$ ratio of 0.03. In addition, the nature of "family dependent" linear free energy relationships is discussed in E and C terms, showing that the two term E and C approach predicts the existence of these relationships and can correlate them without breaking the data into donor types.
Correlations of free energies of neutral donor-acceptor interactions with the enthalpy based E and C parameters shows that the entropies of these interactions is related to enthalpies but not linearly dependent, as required by simple linear free energy relationships. The molecular interpretation of the entropy correlations is shown to have physical significance and is not fortuitous in nature.
The relationships between the more general, three parameter, ect parameters and the E and C parameters are investigated by linear transformation. The results show the ect parameters for neutral bases are not well enough defined to allow their use at this time.
Part Two. Dielectric Time Domain Spectroscopy (TDS) is shown to be applicable to the study of a set of low dopant level ($<$1% Sr$\sp{2+}$), lanthanum orthoferrites with the general formula La$\sb{\rm 1-x}$Sr$\sb{\rm x}$FeO$\sb3$. The complex dielectric response functions are related to electron transfer in locally trapped charged defects in the lattice. The samples show more than one frequency of dielectric loss function in the range from 800MHz to 2 GHz. The barriers to dielectric relaxation are found to be on the order of 0.10eV, much smaller than that expected for conductivity in these systems. The temperature dependent behavior of the dielectric loss function in these systems exhibits nonBoltzmann behavior, suggesting that rate equations based on simple models of static well depths are not applicable.
Issue Date:1987
Description:167 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
Other Identifier(s):(UMI)AAI8803021
Date Available in IDEALS:2014-12-15
Date Deposited:1987

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