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Microfields Induced by Random Compensated Charge Pairs in Ferroelectric Materials

Published online by Cambridge University Press:  01 February 2011

Frank J. Crowne
Affiliation:
RF Electronics Division, Army Research Laboratory, Adelphi, MD 20783-1197, U.S.A.
Steven C. Tidrow
Affiliation:
RF Electronics Division, Army Research Laboratory, Adelphi, MD 20783-1197, U.S.A.
Daniel M. Potrepka
Affiliation:
RF Electronics Division, Army Research Laboratory, Adelphi, MD 20783-1197, U.S.A.
Arthur Tauber
Affiliation:
RF Electronics Division, Army Research Laboratory, Adelphi, MD 20783-1197, U.S.A.
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Abstract

The dc and microwave responses of the BaxSr1-x (X,Y)yTi1-yO3 family of ferroelectric compounds with various substitutional additives X3+, Y5+ are analyzed by combining the random-field technique with the mean-field (Landau-Devonshire) theory of ferroelectricity, along with a self-consistent computation of the dielectric constant of the host material in the presence of the impurity fields. The fields in the material are assumed to arise from charge compensation at the Ti4+ sites, leading to permanent dipoles made up of the resulting positive and negative ions separated by a few lattice constants. It is shown that whereas completely random placement of positive and negative ions generates a Holtsmark distribution of electric field, with infinite second moment and hence extremely large fluctuations in field strength, the association of ionized impurities into permanent dipoles leads to much lower fluctuations in field and a distribution with finite second moment, which makes a self-consistent dielectric constant meaningful.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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