An Experimental Determination of Long Wave-length Phonons and Anomalous Dielectric Behavior in Proustite and Pyrargyrite

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University of Virginia, 1973 - Proustite - 538 pages
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In this work, the Raman, far-infrared, dielectric and group theoretical properties of proustite (Ag3AsS3) and pyrargyrite (Ag3SbS3) were studied. The data and analyses provide information about the long wavelength lattice vibrations of these materials, as well as characterize anomalous dielectric behavior at elevated temperatures (> 250K). The Raman scattering experiments resulted in the observation of 6A(1) and 13E fundamental vibrational modes for both materials. The forward- and back-scattering Raman experiments enabled the longitudinal and transverse optic phonons to be separated (A(1)). Using these results and the Lyddane-Sachs-Teller relation, the low frequency dielectric constant was calculated. An anomalous dielectric behavior at elevated temperatures was attributed to silver ionic conduction in the material and not to a lattice mechanism (ferroelectric phase transition). A model was proposed in which the differences in conductivities of the bulk and space-charge/interface region lead to an interfacial polarization and concomitant rise in the dielectric constant.

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Contents

EXPERIMENTAL
29
INCIDENT OPTICS OF LASER RAMAN SETUP
33
RIGHT ANGLE 90 SCATTERING CONFIGURATION
40

7 other sections not shown

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