Garnet Structure-Activated Warm White Light Phosphors Ca₃Al₂Ge₃O₁₂: Dy³⁺, Eu³⁺ with Ultrahigh Thermal Stability and Tunable Luminescence

Abstract

A series of Ca 3 Al 2 Ge 3 O 12 : xDy 3+ , yEu 3+ phosphors were successfully prepared by the high-temperature solid-phase method. The phase and morphology of the phosphors were studied by means of Rietveld refinement and scanning electron microscopy. The results show that the phase is pure, and the crystal structure is the Ia3̅ d space group. In the Ca 3 Al 2 Ge 3 O 12 : xDy 3+ phosphors, using 380 nm excitation, phosphors showed blue ( 4 F 9/2 → 6 H 15/2 ) and yellow ( 4 F 9/2 → 6 H 13/2 ) emission peaks at 481 and 581 nm, respectively. In Ca 3 Al 2 Ge 3 O 12 : xDy 3+ , yEu 3+ phosphors, the energy transfer was inferred by the spectrum overlap of Dy 3+ and Eu 3+ , and the lifetime attenuation was analyzed from the perspective of dynamics; finally, the band gap structure of the phosphors was analyzed by combining diffuse reflection spectra with the first principle, and the energy transfer mechanism and luminescence mechanism were elaborated by combining theory and practice. The transition from blue white light to red light can be achieved by tuning the range of y in Ca 3 Al 2 Ge 3 O 12 : 0.015Dy 3+ , yEu 3+ . Wherein, when y = 0.07, phosphors, the chromaticity coordinate of warm white CIE is (0.3932, 0.3203), the color temperature is 3093 K, and the warm white light is synthesized. The thermal stability of the synthesized warm white phosphors is 90.1% (423 K), the thermal sensing factors are S amax = 5.51 × 10 −4 K −1 (303 K) and S rmax = 0.0359% K −1 (303 K), and the actual quantum efficiency is IQE = 52.48%. These results prove that Ca 3 Al 2 Ge 3 O 12 : Dy 3+ , Eu 3+ have good application prospects as singlecomponent warm w-LED devices.