Effects of fabrication conditions on mechanical properties and microstructure of duplex β″-Al2O3 solid electrolyte

• The concept of duplex BASEs is presented as a method to lower the ASR for NBBs.
• Duplex BASEs consist of thin dense electrolyte and porous support.
• Strength of converted BASEs shows a different trend from as-sintered samples.
• Cell orientation gives significant impact on strength of duplex BASEs.

Na-beta batteries are an attractive technology as a large-scale electrical energy storage for grid applications. However, additional improvements in performance and cost are needed for wide market penetration. To improve cell performance by minimizing polarizations, reduction of electrolyte thickness was attempted using a duplex structure consisting of a thin dense electrolyte layer and a porous support layer. In this paper, the effects of sintering conditions, dense electrolyte thickness, and cell orientation on the flexural strength of duplex BASEs fabricated using a vapor phase approach were investigated. It is shown that sintering at temperatures between 1500 and 1550 °C results in fine grained microstructures and the highest flexural strength after conversion. Increasing thickness of the dense electrolyte has a small impact on flexural strength, while the orientation of load such that the dense electrolyte is in tension instead of compression has major effects on strength for samples with a well-sintered dense electrolyte.