Doctoral Dissertations

Rasit Koc

Abstract

"The solid solutions of La1-xCaxCr1-yCoyO3 were investigated in an effort to develop an interconnect and cathode materials for solid oxide fuel cells.

Sintering studies were done in air at temperatures below 1500° C. Significant improvements in densification was observed with the substitution of 20 m% Co for Cr due to the presence of a liquid phase. A density of 96 % of theoretical was achieved in air at 1400° C with the substitution of 20 m% Ca for La and 10 m% Co for Cr.

Electrical conductivity DC measurements were made as a function of temperature and oxygen activity. At 1000° C and 1 atm. oxygen the electrical conductivity ranged from 17 to 51 S/cm for La0.9Ca0.1Cr0.9Co0.1O3 and La0.7Ca0.3Cr0.9Co0.1O3, respectively. The conductivity showed thermal activation for all compositions. Under oxidizing conditions the concentration of carriers was directly proportional to the Co and Ca content. All of the compositions showed similar dependence of conductivity on the oxygen activity. Dependence was small at high oxygen activities; as oxygen activity decreased, a break in electrical conductivity at 10-10 atm. and 1000° C was observed, then the electrical conductivity decreased as PO₂1/4. A positive Seebeck coefficient was observed for all the compositions indicating p-type conductivity.

Sintering, electrical conductivity, thermal expansion and stability studies indicate that La1-xCaxCr0.9Co0.1O3 with x = 0.1 - 0.3 appears to be a candidate for SOFC applications"--Abstract, page ii.

Advisor(s)

Anderson, H. U. (Harlan U.)

Committee Member(s)

Moore, Robert E., 1930-2003
Day, D. E.
Sparlin, Don M.
Pringle, Oran Allan

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Ceramic Engineering

Sponsor(s)

United States. Department of Energy. Basic Science Division

Publisher

University of Missouri--Rolla

Publication Date

Fall 1989

Journal article titles appearing in thesis/dissertation

Structural, sintering and electrical properties of the perovskite-type (La, Sr) (Cr, Mn) O3

Pagination

vii, 128 pages

Note about bibliography

Includes bibliographical references.

Rights

© 1989 Rasit Koc, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Thesis Number

T 5938

Print OCLC #

22039312

Electronic OCLC #

1018308141

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