Effect of the Nature of a Sodium-Conducting Solid Electrolyte on the Impedance of Its Interface with the SmCo0.8Ti0.2O3 Oxide Electrode in an Oxygen Atmosphere

Impedance spectroscopy is employed for studying the behavior of the interface of the SmCo_0.8Ti_0.2O₃ semiconducting oxide electrode with a sodium-conducting solid electrolyte (Na⁺–SE) in atmospheres of argon and oxygen. Compounds with the susceptibility to hydration decreasing in the row Na₅TbSi₄O₁₂ Na₃Zr₂Si₂PO₁₂ Na₃Sc₂(PO₄)₃ are used as the Na⁺–SE. Only the systems containing the Na₅TbSi₄O₁₂ solid electrolyte, the grain surfaces of which acquire boundary layers formed by hydration products, are sensitive to oxygen. The exchange current of the electrode reaction O₂ (g) + e O₂ ^– increases from 1.8 to 19 mA/cm² in the temperature interval 250–300°C. The systems with Na⁺–SE that are not prone to hydration remain inactive in the oxygen atmosphere probably due to quick blocking of the active centers by nonconducting products of the secondary chemical reaction Na⁺ + O₂ ^– NaO₂.