Highly Efficient Narrow‐Band Green Emission in LaZn_1‐xMn_xAl₁₁O₁₉ Magnetoplumbite Phosphors toward White LED Application and Optical Thermometer

Abstract Mn²⁺‐doped phosphors with narrow‐band green emission are promising for white light‐emitting diodes (WLEDs) to achieve high color rendering index and efficacy. Here, a series of narrow‐band green‐emitting LaZn_1−xMn_xAl₁₁O₁₉ (0.01 ≤ x ≤ 0.30) magnetoplumbite phosphors (λ_em = 515 nm) with full width at half maximum (FWHM) of ≈26 nm are designed based on highly symmetrical crystallographic structure. These green phosphors exhibit good photoluminescence quantum yield (PLQY) and small thermal quenching (TQ) performance (86%@423 K) under 450 nm blue light excitation. By further heavy doping Mn²⁺ into LaZnAl₁₁O₁₉, a broadband red emission peaking at ≈672–697 nm appears upon blue light excitation due to the Mn²⁺–Mn²⁺ super‐exchange interactions. A dual‐wavelength emission in LaZn_1−xMn_xAl₁₁O₁₉ (0.5 ≤ x ≤ 1.0) phosphors provides thermal‐sensitive emission for ratiometric temperature sensing with good relative sensitivity. Benefitting from the Eu²⁺ → Mn²⁺ energy transfer, the green emission from Mn²⁺ is increased by 26 times, and the internal QY of La_0.97Zn_1−xMn_xAl₁₁O₁₉:0.03Eu²⁺ reaches as high as 88% upon 350 nm light excitation. The efficient blue‐to‐green phosphors are obtained and used as candidates for violet‐excited WLEDs. This study has a guiding role in the development of Mn²⁺‐doped phosphors in mineral structure with photoluminescence control based on high symmetry and Mn²⁺–Mn²⁺ dimers.