Silver-ion conduction pathways in Ag₅IP₂O₇

Abstract

-012Silver-Ion Conduction Pathways in Ag 5 IP 2 O 7 . -The title compound, which is the compound with the lowest AgI content in the quasi-binary AgIAg 4 P 2 O 7 system, is prepared by melting a mixture of AgI and Ag 4 P 2 O 7 and subsequent annealing at 773 K (evacuated tube, 2 h). Ag 5 IP 2 O 7 crystallizes in the orthorhombic space group P2 1 2 1 2 1 with Z = 4. All silver ions are found to be coordinated by both diphosphate and iodide anions. Ag 5 IP 2 O 7 is a moderate Ag + ion conductor with an activation energy of 0.28 eV and a room temp. conductivity of 3·10 −6 Ω −1 cm −1 . The Ag + ion conduction pathways in this solid electrolyte are modeled by the bond-valence technique.

Crystal structures and ionic conductivities of ternary derivatives of the silver and copper monohalides—II: ordered phases within the (AgX)x–(MX)1−x and (CuX)x–(MX)1−x (M=K, Rb and Cs; X=Cl, Br and I) systems

“…The second approach is the bond valence difference method. This technique has recently been used to probe the plausible sites occupied by diffusing ions and, specifically, to investigate the likely conduction pathways for the diffusing ions within both crystalline and amorphous superionics [71][72][73][74][75][76][77][78][79][80]. The next paper in this series will assess the reliability of this approach to probe the structural properties and ionic conduction mechanisms of the various Ag + and Cu + ternary halides and compare this method with the more commonly used MD method.…”

Synthesis, Crystal Structure and Ionic Conductivity of Ag8I2(CrO4)3

“…Selected interatomic distances/Å and angles/° for Ag 8 I 2 (CrO 4 ) 3 . Estimated standard deviations are given in parentheses.Cr ( Similar silver coordination numbers and the corresponding bonding distances have been frequently observed in various silveroxide and silveriodine materials [7][8][9][10][11][12][13][14][15][16][17][18]. The shortest Ag-Ag distance observed is 2.880(1) Å (Ag2-Ag2).…”

“…The structures of both, AgI and RbAg 4 I 5 , have been studied thoroughly, in particular with respect to the disorder of the cation partial structure [7]. Among the good silver ion conductors, there is a class of compounds with compositelike topologies, containing silver iodide, and silver oxyacid salts, like Ag 3 PO 4 , Ag 2 WO 4 , Ag 3 AsO 4 etc., at the same time [9][10][11][12][13][14][15][16]. The incorporation of silver ions in an immobile framework of complex oxoanions has proven to be an effective route to raise the silver ion conductivity.…”

Trapping phosphate anions inside the [Ag4I]3+ framework: Structure, bonding, and properties of Ag4I(PO4)

“…There are only few other examples in the literature [11,12]. Among those, the crystal structure of Ag 5 I(P 2 O 7 ) provides the most similarity with the crystal structure of Ag 4 I(PO 4 ).…”

“…However, there is a certain disorder in the latter framework resulting from a partial occupancy of four of seven silver atomic positions. Such a disorder is believed to be responsible for high ionic mobility in Ag 5 I(P 2 O 7 ) [6,11]. The positional disorder is even stronger in the Ag 16 I 12 (P 2 O 7 ), Ag 8 I 4 (V 2 O 7 ), and Ag 26 I 18 (W 4 O 16 ) compounds, which crystal structures lack straightforward description because of a complex distribution of partially occupied atoms both within the silveriodine frameworks and guest anions [12].…”