Date of Award

Fall 1992

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor

Blumenthal, Robert N.

Second Advisor

Seitz, Martin A.

Third Advisor

Schneider, Susan E.


Present knowledge of transport of charge and mass in fluorite oxides is based on results from polycrystalline materials. To elucidate the transport of charge and mass in single crystalline materials, electrical conductivity and electrochemical measurement were performed in selected oxides with fluorite structure. Based on the four probe conductivity measurements of compositions 9.4, 15, 18, and 21 m% Yttria stabilized Zirconia with fluorite structure and 3m% Yttria Tetragonal Zirconia, with a closely related tetragonal structure in the temperature range of 450 - 1000 ° C, it was found that 9.4 m% Yttria stabilized Zirconia exhibited highest ionic conductivity. The isothermal ionic conductivities as a function of oxygen vacancy concentration were found to be in agreement with the model proposed by Honhke. The lower temperature (<450°C) ionic conductivity, obtained using the impedance spectroscopic technique, showed a departure from the high temperature extrapolation in "formula" vs. 1000/T plots. This was attributed to dopant-vacancy associates formation. The enthalpy of association was estimated to be 0.21 and 0.38 eV for 3 m% Yttria - tetragonal Zirconia and 9.4 m% Yttria stabilized Zirconia, respectively. The contribution of grain boundaries to the total resistance of pure and dense 3 m% Yttria - Tetragonal Zirconia and 8 m% Yttria stabilized Zirconia ceramic samples, was evaluated using the impedance spectroscopic technique. It was observed that grain boundaries made a marginal contribution to the total resistance, only below 500°C. Furthermore, the grain boundary contribution was found to be significant at temperatures below 350°C...



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