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Electrical Conductivity and Seebeck Coefficient of Divalent-Metal-Doped YCrO3

Published online by Cambridge University Press:  28 February 2011

W. J. Weber ,
J. L. Bates ,
C. W. Griffin  and
L. C. Olsen
W. J. Weber
Affiliation:
Battelle Pacific Northwest Laboratories, P. O. Box 999, Richland, WA 99352
J. L. Bates
Affiliation:
Battelle Pacific Northwest Laboratories, P. O. Box 999, Richland, WA 99352
C. W. Griffin
Affiliation:
Battelle Pacific Northwest Laboratories, P. O. Box 999, Richland, WA 99352
L. C. Olsen
Affiliation:
Joint Center for Graduate Study, 100 Sprout Road, Richland, WA 99352
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Abstract

The substitution of divalent metal ions for γ(+3) in γCrO3 results in a charge compensating transition of Cr(+3) to Cr(+4) and the formation of small polarons as charge carriers. The experimentally measured electrical conductivity, σ, and Seebeck coefficient, S, exhibit behavior consistent with a theoretical model developed for small polaron transport in these narrow-band semiconductors. The small polaron transport is a thermally-activated process with a measured activation energy, E, of about 0.18 to 0.25 eV in these materials. Both σ and S increase with temperature and show a near linear dependence on dopant concentration and a strong dependence on dopant (ionic) size. Analysis of the results in terms of the model indicates that Ca is much more effective in polaron formation than any of the other dopants in γCrO3; this is due to the similar ionic size of Ca(+2) and γ(+3) which minimizes the lattice distortion from substitution.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 60: Symposium L – Defect Properties and Processing of High-Technology Nonmetallic Materials , 1985 , 235
Copyright
Copyright © Materials Research Society 1986

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