Multifunctional applications of efficient Mn4+-Doped La2MgNbO6.5 in plant lighting and optical thermometry

To creating versatile light-emitting materials that enable diverse functionalities, a Mn 4+ -activated La 2 MgNbO 6.5 multifunctional phosphor that exhibits excellent comprehensive performance for applications in plant lighting and optical thermometry was synthesized. The crystal structure and luminescent characteristics were systematically analyzed. The synthesized La 2 MgNbO 6.5 :Mn 4+ shows a broadband excitation band spanning 300-500 nm and delivers far-red emission centered near 708 nm, which overlaps with the P FR phytochrome absorption of plants. Furthermore, the enhancement effect of alkali-metal ions on the performance of La 2 MgNbO 6.5 :Mn 4+ has been investigated. The optimized La 2 MgNb 0.994 O 6.5 :0.006Mn 4+ , 0.003Li + phosphor exhibits remarkable improvements in photoluminescence intensity, external quantum efficiency and thermal stability. Its external quantum efficiency reaches an impressive 50.3%, fully meeting the demands of practical applications. An LED device was fabricated by integrating the optimized La 2 MgNb 0.994 O 6.5 :0.006Mn 4+ , 0.003Li + far-red phosphor with a 410 nm chip. Wheat-seedling cultivation under its illumination demonstrated markedly enhanced stem growth, further validating the phosphor's potential as a far-red-emitting material for indoor plant-growth LED lighting. Meanwhile, the excellent temperature-dependent luminescence behavior of the phosphor also renders it promising for optical thermometry. Its nearly linear response trend enables potential practical applications, yielding a high relative sensitivity of up to 3.3656%·K −1 , and a minimum temperature uncertainty as low as 0.0165 K. The results demonstrate that the Mn 4+ -activated La 2 MgNbO 6.5 multifunctional phosphor possesses broad application prospects in both plant lighting and optical thermometry.