Conductivity study by complex impedance spectroscopy of solid solution AgxK1 − xNb4AsO13 (x = 0.2 and 0.62): effect of the substitution of K+ by Ag+ cations on the ionic conduction properties

• Published in: Journal of solid state electrochemistry 2021, Vol.25 (7), p.1987-1997
• Main Authors: Chérif, Saïda Fatma, Amor, Rym Ben, Chérif, Amira, Zid, Mohamed Faouzi
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Cations; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electric properties; Electrochemistry; Energy Storage; Impedance method; Ion currents; Ionic mobility; Lattice parameters; Original Paper; Physical Chemistry; Potassium; Silver; Solid solutions; Substitution reactions
• ISSN: 1432-8488; 1433-0768
• DOI: 10.1007/s10008-021-04976-0

Crystals of Ag 0.2 K 0.8 Nb 4 AsO 13 (I) and Ag 0.62 K 0.38 Nb 4 AsO 13 (II) were synthesized by a solid-state reaction. Both of them crystallize in the orthorhombic system, space group Cmcm with a = 10.469(2) Å, b = 10.403(2) Å, c = 10.047(1) Å and V = 1094.2(3) Å 3 for (I) and a = 10.438(5) Å, b = 10.443(3) Å, c = 10.042(6) Å and V = 1094.6(7) Å 3 for (II). The structural study of the investigated compounds shows that they have a three-dimensional framework. There are tunnels, with hexagonal section, in where Ag + and K + cations are located. The characteristics derived from the structural study, which support good ion mobility, have encouraged us to study the ionic conductivity through the complex impedance method. We have studied the effect of the substitution of potassium cations (r K+ = 1.37 Å) in the Ag 0.2 K 0.8 Nb 4 AsO 13 compound by the silver one (r Ag+ = 1.09 Å) on the structural and electric properties. For the structural point, we remark that the substitution of potassium by silver causes a slight diminution in the lattice parameters, angles and in distances K/Ag–O. For the electrical point, the substitution of potassium by silver induces the reduction of activation energy.