Electrochemical and Degradation Studies on One-Dimensional Tunneled Sodium Zirconogallate + Yttria-Stabilized Zirconia Composite, Mixed Sodium and Oxygen Ion Conductor

Abstract

In recent years, multi-phase materials capable of multi-ion transport have emerged as attractive candidates for a variety of electrochemical devices. Here, we provide experimental results for fabricating a composite electrolyte made up of a one-dimensional fast sodium-ion conductor, sodium zirconogallate, and an oxygen-ion conductor, yttria-stabilized zirconia. The composite is synthesized through a vapor phase conversion mechanism, and the kinetics of this process are discussed in detail. The samples are characterized using diffraction, electron microscopy, and electrochemical impedance spectroscopy techniques. Samples with a finer grain structure exhibit higher kinetic rates due to larger three-phase boundaries (TPBs) per unit area. The total conductivity is fitted to an Arrhenius type equation with activation energies ranging from 0.23 eV at temperatures below 550 °C to 1.07 eV above 550 °C. The electrochemical performance of multi-phase multi-species, mixed sodium- and oxygen-ion conductors, is tested under both oxygen chemical potential gradient as well as sodium chemical potential gradient, before and after reaching equilibrium, are discussed using the Goldman-Hodgkin-Kats (GHK) and the Nernst equation. The total conductivity of the degraded cathode and anode terminals is investigated using electrochemical impedance spectroscopy. The degradation investigation of samples indicates a decrease in conductivity adjacent to the anode terminal, the loss of sodium content, and the formation of β-gallia adjacent to the fuel electrode after ~396h at 1463 K.

The Influence of Sintering Condition on Microstructure, Phase Composition, and Electrochemical Performance of the Scandia- Ceria- Co-Doped Zirconia for SOFCs

“…Conventionally sintered pellets at 1500 °𝐶 and 1600 °𝐶 showed the highest densification followed by a plateau [48]. However, some ceramics oxides showed a reverse densification behavior which after a point density decreases due to partial formation of liquid phase [55]. However, sintering at 𝑇 ≥ 1500 °𝐶 resulted in excessive grain The obtained powder X-ray diffraction (XRD) patterns of the as-sintered pellets at 1000 °𝐶 to 1650 °𝐶 for 6 hours were collected at room temperature and presented in a comparative stack plot in figure 5.…”