Site Preference-Driven Mn⁴⁺ Stabilization in Double Perovskite Phosphor Regulating Quantum Efficiency from Zero to...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Manganese (Mn) luminescence is crucial, particularly the tetravalent state (Mn4+) for far-red emissions.
• Double perovskite structures (A2B'B″O6:Mn4+) are promising for Mn4+ luminescence, with Mn typically substituting at the B″ site.
• Some Mn-doped perovskites, like Ca2MgWO6:Mn, exhibit weak or no luminescence, indicating challenges in stabilizing Mn4+.

Purpose of the Study:

• To investigate a cation-pair co-substitution strategy to enhance Mn4+ luminescence in double perovskite materials.
• To modify the crystal structure and Mn site occupancy to improve the stability of the tetravalent manganese state.
• To achieve highly efficient far-red emission from Mn-doped oxide phosphors.

Main Methods:

• A cation-pair co-substitution strategy was employed, replacing 2Ca2+ with Na+–La3+ in Ca2MgWO6 to form Ca2-2xNaxLaxMgWO6:Mn.
• Structural analysis was performed to observe lattice distortions, including changes in [MgO6] and [WO6] octahedra.
• Photoluminescence spectroscopy was used to evaluate luminescence properties and quantum efficiencies.

Main Results:

• The cation-pair co-substitution induced significant structural distortion and shifted Mn site occupancy from Mg2+ to W6+ sites.
• This modification enhanced the effective Mn4+/Mn2+ concentration, transforming nonluminescent materials into highly efficient emitters.
• The optimal CaNa0.5La0.5MgWO6:0.9%Mn4+ phosphor achieved an internal quantum efficiency of 94% and external quantum efficiency of 82%.

Conclusions:

• The cation-pair co-substitution strategy effectively stabilizes Mn4+ in oxide phosphors, enabling efficient far-red emission.
• Modifying Mn site occupancy is critical for rational design of Mn4+-activated red phosphors.
• This approach offers a new perspective for developing high-performance Mn4+-doped phosphors.