Anomalous AgI composition dependence of the thermal and dielectric properties of AgI-Ag2O-P2O5 glasses: evidence for the formation of amorphous AgI aggregate regions as dominating the fast Ag+ ion conduction

摘要

Heat capacities of (AgI)(x)(Ag3PO4)(1-x) glasses with x = 0.70 and 0.80 were measured to estimate the jump, Delta C-p, in the beta-glass transition due to freezing of the Ag+ ion rearrangement. Dielectric relaxation properties of (Delta gI)(x)(Ag2PO3.5)(1-x) with x = 0, 0.20, and 0.40 and (AgI)(x)(Ag3PO4)(1-x) glasses with x = 0.30 and 0.40 were examined to estimate the activation energies, Delta epsilon(a), along the conduction path. Delta C-p was found to appear only at larger x than a critical value x(c) = 0.60 for (AgI)(x)(Ag3PO4)(1-x) glasses. x(c), depending on the structure of the glass network former, is larger than the values of 0.35 and 0.54 for (AgI)(x)(AgPO3)(1-x) and (AgI)(x)(Ag2PO3.5)(1-x), respectively, glasses. Delta epsilon(a) was found to show its inflection at around the respective x(c) values for the (AgI)(x)(Ag3PO4)(1-x) and (AgI)(x)(Ag2PO3.5)(1-x) glasses. These observations are discussed to support the 'amorphous AgI aggregate' model for the fast Ag+ ion conduction path.