Enhancement of Red Luminescence in Eu ³⁺ ‐Concentrated EuNa ₂ Mg ₂ V ₃ O ₁₂ Phosphor via La ³⁺ Co‐Doping

Garnet‐type vanadates are promising host materials for rare‐earth activators due to their high emission efficiency, good compatibility, and low cost. However, the practical application in lighting is often limited by concentration quenching and poor thermal stability. In this work, we investigate the effect of La 3+ doping on the microstructure and luminescence properties of the fully Eu 3+ ‐concentrated vanadate EuNa 2 Mg 2 V 3 O 12 . La 3+ ‐doping preserves the single‐phase structure while modifying the local environment of Eu 3+ ions. Through laser site‐selective spectroscopy, we identify two distinct Eu 3+ luminescence centers: a dominant B ‐site center with D 2 symmetry and a minor A ‐site center associated with defect clusters. La 3+ doping effectively suppresses the A ‐site centers and promotes a more uniform distribution of Eu 3+ , reducing nonradiative decay. As a result, the quantum efficiency of Eu 0.7 La 0.3 Na 2 Mg 2 V 3 O 12 reaches 72.5%, a 20% improvement over the undoped sample. The thermal activation energy also increases from 0.413 to 0.472 eV. A prototype LED fabricated with the optimized phosphor exhibits bright red emission ( x = 0.65, y = 0.34) under near‐UV excitation. When combined with commercial green and blue phosphors, the device produces standard white light. These findings demonstrate that La 3+ doping is an effective strategy for enhancing the performance of highly concentrated Eu 3+ phosphors in optoelectronic applications.