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Dielectric Behavior and Phonon Damping in Low-Dielectric Constant Perovskite Materials
Published online by Cambridge University Press: 10 February 2011
Abstract
We have carried out a comparative study of the dielectric losses in some complex perovskites with both 1:1 and 1:2 compositions of the B ions, namely, SrAl1/2Nb1/2O3 (SAN), SrAl1/2Ta1/2O3 (SAT) and BaMg1/3Ta2/3O3 (BMT). The samples were prepared in two forms, viz. ceramics and single-crystal fibers, the latter were grown by laser heated pedestal growth technique (LHPG). All of these materials possess low dielectric constants, low losses and high Q values. In contrast to relaxor ferroelectrics, that as a rule exhibit broad features in their Raman spectra, SAN, SAT and especially BMT have very narrow phonon lines in the Raman spectra. A linear correlation is found between the microwave dielectric losses and the width of first order phonon lines in a sequence of BMT → SAT → SAN ceramics with increasing phonon damping. Moreover, the phonon damping decreases in materials with non-close-packed structure where there is enough space for undisturbed phonon vibrations. The problem of charge compensation in compounds with the Bsite disorder is also discussed.
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- Copyright © Materials Research Society 1998