The explanation of electrical properties changes under NH3 and H2 containing atmospheres in risen temperatures of ceria- and zirconia-based solid electrolytes by means of electrochemical impedance spectroscopy

Abstract

In the presented research, commercial powders of nominal compositions: Ce0.8Gd0.2O1.9, Sc0.1Ce0.01Zr0.89O1.95, Sc0.09Yb0.01Zr0.9O1.95 structural and electrochemical properties were investigated. The X-ray diffraction of the specimens at room temperature showed a cubic phase. Electrical properties studies over a wide range of frequencies (0.1 Hz to 32 MHz) and temperature (200–600 °C) were analyzed using impedance spectroscopic technique in different atmospheres (synthetic air, 3000 ppm NH3 in argon, 10% H2 in argon). The impedance plane plot shows semicircle arcs at different temperatures and electrical equivalent circuit have been proposed to analyze the impedance results. Basing on comparison of the spectra in different atmospheres the reactions on the three-phase boundaries were proposed as well as the conduction mechanisms of the electrolytes were described. The material based on ceria is mixed ionic-electronic conductor, while in zirconia-based materials electrical conduction is realized by oxygen ion carriers. The electrochemical properties of the powders were compared from the applicative point of view as a candidate for element in fuel cells and gas sensors.