Influence of yttrium and zirconium as solid solutions and pinning points on the obtaining of sodium-beta’’-alumina electrolytes

Reference	Presenter	Authors (Institution)	Abstract
06-209	Daisy Catharina Rodrigues	Rodrigues, D.C.(Universidade Federal de São Carlos); Souza, D.P.(Universidade Federal de São Carlos);	The concerns about the environmental consequences of greenhouse gas emissions, the unbridled use of fossil fuels and the limitations of renewable energy sources have renewed the interest in the use of electrical energy storage. The ZEBRA battery is an efficient electrochemical energy storage device with high energy density. It uses nickel chloride as positive electrode and sodium as negative electrode, separated by a beta’’-alumina solid electrolyte. This has been considered one of the key technologies for insertion into the economic market of electric vehicles and for stationary energy applications. However, due to high internal resistance of this device causes an intense search for new materials for the reduction of this issue. Sodium-beta’’-alumina solid electrolytes, due to its high ionic conductivity for sodium ions, are among the most promising oxide ionic conductors for the ZEBRA battery, operating at temperatures of approximately 300 ºC. However, the greatest difficulty in using sodium-beta’’-alumina is related to the instability of this phase at higher sintering temperatures in excess of 1300 ºC. The ceramic processing of this electrolyte can influence the final mechanical and electrical properties of the material. In this work, the focus was to balance the mechanical and electrical properties through the reduction of microstructure defects. Sodium-beta’’-alumina electrolytes of composition 8.85% ${\mathrm{Na}}_2\mathrm{O}$·0.75% ${\mathrm{Li}}_2\mathrm{O}$·90.4% ${\mathrm{Al}}_2{\mathrm{O}}_3$ (wt%) were obtained by mechanical mixing using yttrium and zirconium as solid solutions and pinning points. The samples were sintered at temperatures of 1600 °C/0, 10 and 20 min, following a heat treatment at 1475 °C/120 min, and at 1500, 1475, 1400 and 1300 ºC/120 min. Analysis of density, microstructure and electrical conductivity were performed. The microstructure, and consequently the electric conductivity and mechanical strength were sensitive to sintering profile, yielding promising results.
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