Correlated Na+ Ion Migration Invokes Zero Thermal Quenching in a Sodium Superionic Conductor-type Phosphor

Among the many potential Eu2+-activated sodium superionic conductor (NASICON)-based host materials, the Sc3+-based NASICON phosphor (Na3Sc2(PO4)3:Eu2+) is a promising phosphor material for high-power lighting applications owing to its unusual thermal stability at elevated temperatures. It has previously been shown that negative thermal quenching (TQ) can be tailored to zero TQ depending on the Eu2+ concentration. However, the obtained zero-TQ composition has low photoluminescent quantum yields, which hinders its applicability to high-power lighting. Herein, we report a holistic study of the tuning of thermal stability from negative TQ to zero TQ while preserving the original emission efficiency by introducing Lu3+ ions in Na3Sc2(PO4)3:Eu2+. Furthermore, we fabricated a high-power white light-emitting diode using optimized Lu3+-doped Na3Sc2(PO4)3:Eu2+ as the blue component, delivering a high color-rendering index value of 90 with a high luminous efficiency value of 25 lm/W obtained at a flux current of 1000 mA. Therefore, the findings of this work provide novel scientific insights into the importance of structure–property relationships in designing highly efficient thermally stable phosphors for high-power lighting applications.