Ionic Conductivities of Molten CuI and AgI-CuI Mixtures

Abstract

Ionic conductivities σ for molten CuI and AgI-CuI mixtures were measured in the temperature ranges of approximately 580-800 and 500-850 °C, respectively. The value of σ for molten CuI in the range is smaller than that for molten CuBr and CuCl. σ for molten AgI-CuI mixtures decreases with increasing CuI-concentration. The activation energies E a for molten AgI-CuI system were determined from the analysis of temperature dependence of σ by using the by Arrhenius type equation. E a for molten AgI-CuI gradually increase with increasing CuIconcentration.AgI and CuI are well known as superionic conductors. In these materials, Ag and Cu ions can migrate through the interstitial space of the sublattice formed by I ions in high temperature solid phase under the melting point [1][2][3]. It is also known that AgI-CuI mixtures form solid solutions, and both Ag and Cu ions can migrate through the anion sublattice in the high temperature superionic phase [4,5]. In the superionic phase of AgICuI mixtures, I ions form lattice, and the lattice type depends on the cationic concentration (b.c.c. for Ag-rich region and f.c.c. for Cu-rich region) [4,5]. Although the structure and ionic conductivity of AgI-CuI solid solutions have been investigated by several scholars using experimental and simulation techniques [5][6][7], those in molten phase have not been investigated yet.In the present study, we report the ionic conductivities of molten CuI and molten (AgI) 1-x (CuI) x mixtures measured by the four-probe method, and discuss the detailed information on ionic conduction with activation energies.AgI and CuI powder samples were purchased from Wako Pure Chemical Industries. Samples of (AgI) 1-x (CuI) x (x = 0.2, 0.5, 0.8) mixtures were prepared by mixing powder materials of AgI and CuI. A mixture sample was put into an original quartz cell with 4 mm * tahara@sci.u-ryukyu.ac.jp