IntroductionNear-infrared (NIR) luminescence with emission wavelengths ranging from 700 nm to 1100 nm has attracted much attention in the fields of nondestructive testing, biometrics, and night vision. In this paper, high-temperature solid-phase method was used to synthesize Cr³⁺ single-doped and Ce³⁺, Cr³⁺ co-doped Y₂CaAl₄SiO₁₂ luminescent materials. Under 438 nm light excitation, Cr³⁺ could produce a near-infrared broadband emission at 740 nm and R-line narrowband emission at 690 nm. The quantum efficiency of mono-doped Cr³⁺ was calculated to be 24%, and the crystal field intensity was calculated to be 2.429 by excitation spectral analysis. The thermal stability and the luminescence intensity of Y₂CaAl₄SiO₁₂: Cr³⁺ were analyzed by variable-temperature spectroscopy. In addition, Y₂CaAl₄SiO₁₂: Ce³⁺, Cr³⁺ luminescent materials were also prepared, and the luminescence intensity and the quantum luminescence efficiency of Y₂CaAl₄SiO₁₂: 0.005Ce³⁺, 0.007Cr³⁺ were analyzed.MethodsIn accordance with the stoichiometric ratios, Y_2-xCaAl₄SiO₁₂: xCe³⁺ (where x = 0.001-0.011 mol) and Y₂CaAl_4-ySiO₁₂: 0.005 Ce³⁺, y Cr³⁺ (where y = 0.001-0.011 mol) were prepared via solid-state reactions with raw materials of CaCO₃, Cr₂O₃, CeO₂, Al₂O₃, SiO₂, and Y₂O₃. The mixture with anhydrous ethanol was then ground in a mortar. Subsequently, the ground material was dried in an oven at 80 ℃ before being transferred to a square crucible for sintering in a reducing atmosphere at 1550 ℃ for 4 h. Afterwards, the sample was removed and allowed to cool to room temperature for the coming analysis.Results and discussionY₂CaAl₄SiO₁₂: Cr³⁺ belongs to a cubic structure, the space group is , the number of molecules Z=8. The optimal doping concentration of Y₂CaAl_4-ySiO₁₂: yCr³⁺(y = 0-0.01) is 0.007, and the quenching mechanism of concentration is dipole-dipole interaction. After co-doping of Cr³⁺ and Ce³⁺ (Cr³⁺ is 0.007), the luminescence intensity is about 3 times greater than that of single-doped Cr³⁺, and the quantum efficiency is 45%. This indicates that the co-blending improves the luminescence performance of the material. When co-doped with Y₂CaAl₄SiO₁₂:Ce³⁺ and Cr³⁺, the luminescence properties of the sample can reach 77.6% of the room temperature at 423 K (150 ℃), and the thermal stability is good.ConclusionsNear-infrared luminescent materials of Y_2-xCaAl₄SiO₁₂: Cr³⁺ and Y₂CaAl₄SiO₁₂: Ce³⁺, Cr³⁺ were synthesized via soild-state reactions. The luminescence properties and thermal stability of the samples were thoroughly analyzed, and Ce³⁺ was incorporated as a sensitizer to investigate the energy transfer mechanism between Ce³⁺ and Cr³⁺ within the matrix. The results indicated that Y₂CaAl₄SiO₁₂ exhibits a garnet structure, Cr³⁺ generated a broad near-infrared emission spectrum peaking at 740 nm alongside a sharp peak at 690 nm, achieving a quantum efficiency of 24% when doped alone. Y₂CaAl₄SiO₁₂: Ce³⁺, Cr³⁺ prepared had an energy transfer from Ce³⁺ to Cr³⁺. The energy transfer mechanism of this system was elucidated through IS0 and c fitting analyses. The luminous intensity of Y_1.995CaAl_3.993SiO₁₂: 0.005Ce³⁺ and 0.007Cr³⁺ was threefold greater than that of Y₂CaAl_3.993SiO₁₂: 0.007Cr³⁺. At this juncture, the quantum efficiency for co-doping reached 45%. When y was 0.011, the energy transfer efficiency measured was 30.01%. The thermal stability of Y₂CaAl₄SiO₁₂: 0.007Cr³⁺ revealed that its luminous intensity at 150 ℃ retained 77.6% of its value at room temperature, with a thermal activation energy calculated of 0.207 eV. This work could provide essential data for future applications of this material.