Migration pathways in Ag-based superionic glasses and crystals investigated by the bond valence method

Abstract

The bond valence technique has been applied on reverse Monte Carlo produced structural models of Agbased superionic glasses and crystals. The results for the ͑AgI͒ 0.75 -͑Ag 2 MoO 4 ͒ 0.25 and ͑AgI͒ 0.6 -͑Ag 2 O-2B 2 O 3 ͒ 0.4 glasses show the importance of including Ag sites with a high oxide coordination for the long-range mobility. The majority of the Ag ϩ ions belonging to the long-range conduction pathways is coordinated to both O and I Ϫ , and the pathways including only iodide coordinated sites are restricted to very local regions of a few Å. The most important finding of the present study is that the ionic conductivity as well as its activation energy can be determined directly from the ''pathway volume'' ͑i.e., the volume fraction of the percolating pathway cluster͒ of the structural models. The conductivity pathway volume relation is found to hold for glassy and crystalline conductors ͑including their temperature dependencies͒, whose conductivities differ by more than 11 orders of magnitude.

A microscopic interpretation of the bulk anomalies in AgI–Ag2O · 2B2O3glasses

“…Carlo results [9]. We also showed that our model takes into account some composition anomalies observed in borate and phosphate glasses.…”

“…Since the addition of AgI to the oxyanion matrix leads to the progressive formation of On the other hand, it is accepted that the glass forming network may play an important role for low AgI content due to the non-bridging oxygens, or to intermediate range structure [9]. (coordination number, Z=4) [12].…”

Nano-scale structural inhomogeneities of CuI–Cu2MoO4 superionic conducting glass observed by high resolution transmission electron microscopy

“…Actually some structural models are proposed based on the existence of 'clusters' or 'microdomains' of AgI or CuI with tetrahedral coordination, which is dispersed in the host matrix constructed with oxyanions [13,14]. Numerous structural studies were performed so far to clarify the medium-range structure by various experimental techniques.…”

Neutron diffraction study of Li 4 Ti 5 O 12 at low temperatures

“…The presence of well-defined cage in the bondvalence pathway can be attributed to the packing density: in densely packing systems one may expect that the ions will migrate along narrow pathways, whereas in open crystal structures (e.g. zeolites) the guest ions will not reside at the center of large channels, but will generally prefer to move along the walls of the channels [45].…”