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Ionic transport in AgI‐HgS‐As 2 S 3 glasses: Critical percolation and modifier‐controlled domains
Author(s) -
Kassem Mohammad,
Khaoulani Sohayb,
Bychkov Eugene
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15414
Subject(s) - silver iodide , ionic bonding , percolation (cognitive psychology) , ionic conductivity , ion , activation energy , analytical chemistry (journal) , iodide , chemistry , coordination number , materials science , inorganic chemistry , nanotechnology , electrode , organic chemistry , layer (electronics) , chromatography , neuroscience , electrolyte , biology , silver halide
Abstract Electrical measurements, dc and ac , show that (AgI) x (HgS) 0.5‐ x /2 (As 2 S 3 ) 0.5‐ x /2 glasses, 0.0 ≤ x ≤ 0.6, exhibit drastic changes in ionic conductivity σ i with silver iodide additions. The ionic transport increases by 13 orders of magnitude with increasing silver content from ~0.002 to ~23 at.%, and the activation energy decreases from 1.05 to 0.35 eV . Two distinctly different ion transport regimes above the percolation threshold concentration, x c ≈ 30 ppm, were distinguished. The critical percolation regime at low silver content (≤ 2‐5 at.% Ag) is characterized by a random distribution of silver‐related entities and obeys a power‐law composition dependence of σ i . The ion transport parameters depend on the host network connectivity, represented by the average coordination number , via the critical fictive temperature T 0 ; the calculated T 0 value is comparable to the glass transition temperature for the glassy (HgS) 0.5 (As 2 S 3 ) 0.5 host matrix. In contrast, in the modifier‐controlled domain, the silver‐related entities are nonrandomly distributed. The high Ag + ionic mobility results from interconnected tetrahedral (AgI 2/2 S 2/2 ) n chains in the silver iodide content range 0.2 < x ≤ 0.5, and from 2D layers (Ag 3/3 I 3/3 ) n or 3D mixed tetrahedral subnetwork (AgI 3/3 S 1/2 ) in the range x > 0.5.