Fast-quenched Na₂Si₂O₅ stability and properties in crystalline composite

The sinter-crystallisation method of as-casted glass-based materials is effective for obtaining glass ceramics with different functional properties. We here report the microstructural, chemical composition, and ion dynamics of a fast Na-ion conductor Na₂Si₂O₅ synthesised by the melt-quenching route. The parent glass is treated under different temperatures and crystallisation times. The analysis shows that the electrical properties strongly depend on the material's microstructural properties and thermal history. The fast-quenched materials achieve greater stability and electrical properties, outperforming the solid-state reaction methods and SrSiO₃-Na₂Si₂O₅ composites. We show that the crystalline regions in the sintered material act as nucleation centres for the recrystallised Na₂Si₂O₅ phase, affecting the conductivity. The melt-quenched material shows a high conductivity of 10⁻¹ S cm⁻¹ at 750°C. Furthermore, the recrystallisation process of Na₂Si₂O₅ is reversible, leading to a facile regeneration of the ionic properties.