Thermally stable Cr³⁺-activated silicate phosphors for plant-growth LEDs and three-mode optical thermometry

The structural, optical and temperature-dependent luminescence properties of Y₂Mg₂Al₂Si₂O₁₂:Cr³⁺ phosphors were investigated for their multifunctional applications. The as-prepared phosphors exhibited an intense far-red emission band around 600-850 nm with a peak at 687 nm, which matches well with the absorption band of plant phytochromes. Importantly, the optimized sample showed excellent thermal stability and its emission intensity at 423 K maintained about 77% of that at 298 K. The potential application of the phosphors in plant-growth LED devices was also demonstrated. Furthermore, owing to the unique thermal quenching behavior of Cr³⁺, a three-mode luminescent thermometry system was designed based on fluorescent intensity (FL), fluorescent intensity ratio (FIR), and full width at half maximum (FWHM). The maximum temperature relative sensitivity (S_r) of each mode could reach 2.74% K^-1, 1.09% K^-1, and 1.47% K^-1, respectively. These results indicate that the Y₂Mg₂Al₂Si₂O₁₂:Cr³⁺ phosphors have potential applications for plant growth and optical thermometry.