New apatite‐type oxide ion conductors Ce9.33+xSi6O26+δ: Structures, phase stabilities, electrical properties, and conducting mechanisms

Abstract

Abstract Apatite‐type rare earth silicate with high oxygen ion conductivity are attractive materials for their wide potential applications, such as being used in solid oxide fuel cells as electrolytes. Herein, a series of new apatite‐type oxide ion conductors Ce9.33+xSi6O26+δ (x = 0.43, 0.67, 1.03) have been prepared, with their phases, stabilities, electrical properties, and conducting mechanisms been thoroughly studied. The results reveal that these materials are stable under inert or reducing atmospheres, but decomposed under an oxidizing environment at elevated temperatures. The combined alternative current and directive current techniques reveal dominating oxide ion conductions and minor electronic conductions in them. The bond‐valence‐based method is applied to investigate the possible oxide ion migration pathways and disclose the main contribution from interstitial oxygens, which locate between two neighboring tetrahedral SiO4 units and enable the oxide ion transporting among them along the c‐axis direction, whereas the intrinsic channel oxygens show an inferior responsibility for the oxide ion conductivities.

Keywords

• apatite‐type
• Ce9.33+xSi6O26+δ
• conducting mechanisms
• oxide ion conductor