Ionic transport and atomic structure of AgI-HgS-GeS2 glasses
Résumé
Quasi-ternary (AgI) x (HgS) 0.5−x/2 (GeS 2) 0.5−x/2 glasses, 10 −4 ≤ x ≤ 0.6 were studied over a wide composition range covering nearly 4 orders of magnitude in the mobile cation content. The glasses show a remarkable increase of the ionic conductivity by 12 orders of magnitude and exhibit two drastically different ion transport regimes: (i) a power-law critical percolation at x 0.04, and (ii) a modifier-controlled conductivity, exponentially dependent on x 0.1. Using Raman spectroscopy and high-energy X-ray diffraction supported by DFT modelling of the Raman spectra we show that the glass network is essentially formed by corner-sharing CS-GeS 4/2 tetrahedra. Mercury sulfide in glasses is dimorphic. The majority of Hg species (70 % at x < 0.2) exist as twofold coordinated (HgS 2/2) n chains. Silver species have mixed (2I + 2S) tetrahedral environment forming either edge-sharing ES-Ag 2 I 2 S 4/2 dimers or corner-sharing (CS-AgI 2/2 S 2/2) n chains. The relationship between the ionic transport and atomic structure of the glasses is discussed.
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Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification
Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification