Synthesis and Electrochemical Study of Multi-Phase, Multi-Species Ion Conductor Sodium beta"-Alumina (BASE) + 20SDC Using a Vapor-Phase Process

TL;DR

This study demonstrates a cost-effective vapor-phase process to synthesize multi-phase sodium and oxygen ion conductors with enhanced conductivity and reduced fabrication time, advancing materials for electrochemical devices.

Contribution

It introduces a novel vapor-phase fabrication method for multi-phase Na-beta''-alumina+20SDC with improved conductivity and faster processing compared to traditional techniques.

Findings

Total conductivity increased threefold in multi-phase samples.

Finer grains lead to faster ion transport kinetics.

Fabrication time reduced by 60% compared to previous methods.

Abstract

The recent emergence of multi-species multi-phase materials provides intriguing opportunities to maximize electrochemical performance in various electrochemical devices. This work summarizes the current understanding of the coupled transport reactions in multi-phase multi-species ionic conductors. We also provide experimental results of the fabrication of multi-phases Na-beta"-alumina+20mol% Scandia Doped Ceria(20SDC) as simultaneous sodium and oxygen ion conductor by a cost-effective vapor phase process demonstrating higher conductivity achieved in a much shorter time than other published results. In this study, two-phase contiguous composites of Al2O3+20SDC are fabricated by conventional ceramic processing and sintering in the air at 1400C 1500C, and 1600C, for 3 hours. The samples are heat-treated while exposed to a sodium oxide vapor source at different time lengths. The conversion mechanism involves coupled transport of sodium ions through newly formed Na-beta"-alumina and oxygen ions through 20SDC. The experimental data are analyzed using diffraction and spectroscopy methods. The samples with finer grains show faster kinetics compared to coarse microstructures due to the presence of more extended triple-phase boundaries (TPB). As a result, the total conductivity of the multi-phase sample compared to that of pure 20SDC is improved by three times, while fabrication time is decreased by 60% compared to Na-beta"-alumina+YSZ.