Mn⁴⁺-activated LuMg₃SbO₇ red phosphors for highly sensitive optical temperature sensing and plant-growth applications

The development of multifunctional deep-red phosphors for optical thermometry and plant lighting still faces considerable challenges. In this work, a series of novel red-emitting phosphors LuMg₃SbO₇:xMn⁴⁺ (0 ≤ x ≤ 0.030) were synthesized by a conventional high-temperature solid-state reaction. XRD and SEM results confirm the high phase purity and uniform element distribution, with negligible effect of Mn⁴⁺ doping on the host structure. The phosphors show broad Mn⁴⁺ absorption (200-600 nm) suitable for UV LED excitation and yield intense deep-red emission (600-800 nm) under UV irradiation. Concentration quenching is observed above x = 0.010, which is ascribed to the electric dipole-quadrupole interaction between Mn⁴⁺ ions. The optimal sample LuMg₃SbO₇:0.010Mn⁴⁺ exhibits excellent luminescence properties with IQE = 92.8% and EQE = 43.1% and realizes dual-mode optical thermometry with maximum relative sensitivities of 4.43% K^-1 (lifetime) and 0.48% K^-1 (FWHM). The fabricated LED device presents an emission peak at 683 nm, well matching the absorption of phytochrome Pfr. These results demonstrate that LuMg₃SbO₇:Mn⁴⁺ is a promising multifunctional red phosphor for optical thermometry and plant growth lighting.