Glass formation and ionic conduction in the M 2SGeS 2 (M = Li, Na, Ag) systems

Abstract

GeS 2 forms stable glasses with Li 2S, Na 2S, Ag 2S in a large range of composition (from 1–0.5 in molar ratio of GeS 2). Raman spectra are presented and a vibrational assignment in terms of bridging and non-bridging sulfur has been made. The electrical conductivity of these glasses has been measured over a range of temperature (−20–150°C) and composition by the complex-impedance diagram method. At high alkali or silver sulfide content and at 25°C they present a good ionic conductivity (>10 −5(ω cm) −1 for Li glasses, >10 −6(ω cm) −1 for Na glasses, >10 −3(ω cm) −1 for Ag glasses). This result may be due to the large polarisability of the sulfur atoms. A new arrangement with 3 electrodes on solid electrolytes is used for testing the electrochemical stability range of these glasses. A value of 4 V with a 0.05 mA cm −2 current can be estimated.