An Experimental Determination of Long Wavelength Phonons and Anomalous Dielectric Behavior in Proustite and Pyrargyrite,
FRANKFORD ARSENAL PHILADELPHIA PA
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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 6A1 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 A1. 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-chargeinterface region lead to an interfacial polarization and concomitant rise in the dielectric constant.
- Solid State Physics