Sintering of sodium conducting glass ceramics in the Na₂O-Y₂O₃-SiO₂-system

A solid electrolyte is a core component for the development of low temperature sodium batteries with metallic Na-anode. The Na₅YSi₄O₁₂ (N5) composition in the Na₂O-Y₂O₃-SiO₂ system shows a high ionic conductivity comparable to NASICON or β-Al₂O₃. Up to date glass ceramic solid electrolytes of this type have been mainly prepared by crystallization of monolithic, molten glass components. We show that this material can be processed via the glass-ceramic powder route starting with a glass powder. A glass with a composition according to the stoichiometry of the Na₅YSi₄O₁₂-phase and tailored by addition of P₂O₅ allows the separation of sintering and crystallization of the glass powder resulting in dense microstructure. Thermophysical properties and phase content have been correlated with ionic conductivity. The densification and crystallization are completed at temperatures below 1100 °C. Grain conductivities up to 0,18 mS cm⁻¹ at room temperature in sintered glass ceramic microstructures are demonstrated.