Local structure and influence of bonding on the phase-change behavior of the chalcogenide compounds K1-xRbxSb5S8
Date
2007Author
Wachter, J. B.Chrissafis, K.
Petkov, V.
Malliakas, C. D.
Bilc, D. I.
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Paraskevopoulos, K. M.
Mahanti, S. D.
Torbrügge, T.
Eckert, H.
Kanatzidis, M. G.
Source
Journal of Solid State ChemistryVolume
180Pages
420-431Google Scholar check
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KSb5S8 and its solid solution analogs with Rb and Tl were found to exhibit a reversible and tunable glass→crystal→glass phase transition. Selected members of this series were analyzed by differential scanning calorimetry to measure the effect of the substitution on the thermal properties. The solid solutions K1-xRbxSb5S8 exhibited clear deviations in melting and crystallization behavior and temperatures from the parent structure. The crystallization process of the glassy KSb5S8 as a function of temperature could clearly be followed with Raman spectroscopy. The thermal conductivity of both glassy and crystalline KSb5S8 at room temperature is ∼0.40 W/m K, among the lowest known values for any dense solid-state material. Electronic band structure calculations carried out on KSb5S8 and TlSb5S8 show the presence of large indirect band-gaps and confirm the coexistence of covalent Sb-S bonding and predominantly ionic K(Tl)⋯S bonding. Pair distribution function analyses based on total X-ray scattering data on both crystalline and glassy K1-xRbxSb5S8 showed that the basic structure-defining unit is the same and it involves a distorted polyhedron of "SbS7" fragment of ∼7 Å diameter. The similarity of local structure between the glassy and crystalline phases accounts for the facile crystallization rate in this system. © 2006 Elsevier Inc. All rights reserved.