Realizing an impressive red-emitting Ca9MnNa(PO4)7 phosphor through a dual function based on disturbing structural confinement and energy transfer

Abstract

In the field of white LEDs, the research and development of red phosphors have been confronting a challenge. In this paper, a novel red-emitting Ca₉MnNa(PO₄)₇ (CMNPO) phosphor, whose emission was attributed to the ⁴T₁(⁴G)–⁶A₁(⁶S) transition of Mn²⁺ ions, was prepared by a high-temperature solid-state reaction. We utilized a chemical co-substitution strategy to optimize the luminescence properties and realize an impressive red emission in our CMNPO phosphor. The introduction of Zn²⁺/Mg²⁺ into CMNPO could break the intrinsic structural confinement of Mn²⁺, which improved the red emission from Mn²⁺ in the narrow confines. The novelty of this work lies in realizing an efficient red phosphor by doping trace amounts of Eu²⁺. By partially replacing Mn²⁺ ions with trace amounts of Eu²⁺, we obtained a CMNPO phosphor that emitted a dazzling red light, and the quantum yield reached up to 82%. The intensity dependence of this red emission on the trace amounts of doped Eu²⁺ was quantitatively analyzed. The substitution of Eu²⁺ ions played a dual role in improving the luminescence properties, not only disturbing the structural confinement of Mn²⁺ but also transferring energy to Mn²⁺ efficiently. By employing it as a red phosphor, we fabricated various high-performance white LEDs with low correlated color temperatures (4642–4956 K) and high-color-rendering indices (80.5–83.4). These findings show the potential promise of the CMNPO phosphor as a red phosphor in warm white LEDs and open up new avenues for the exploration of novel red-emitting phosphors.