Selectivity of Mn2+ ion occupancy and energy transfer of Ce3+ → Mn2+ ions in garnet solid solution

Abstract

As a luminous center, Mn²⁺ has the advantages of high efficiency, safety, and low cost, and has been widely used to improve the color rendering index of garnet structured phosphors. Although the position of Mn²⁺ in garnet structures and its corresponding spectrum have been widely discussed, there is no convincing conclusion. In this paper, the selectivity of Mn²⁺ ion occupancy in the Y₃Al₅O₁₂:0.1Ce³⁺,yMn²⁺ (y = 0–0.22) garnet structure and their corresponding emission spectra were determined. At low substitution density, Mn²⁺ ions (y = 0–0.007) easily replace Al³⁺ ions in the octahedron and emit 590 nm red light under 450 nm blue light excitation, which were determined by calculating the formation energy of the (Mn/Al) and (Mn/Y) local coordination and powder XRD analysis. Upon increasing the Mn²⁺ concentration from 0.007 to 0.22, the emission light with a peak at 750 nm gradually appears. Meanwhile, the effect of Y³⁺ ions on the energy transfer of Ce³⁺ → Mn²⁺ in (Lu_1−xY_x)₃Al_4.8Si_0.2O₁₂:0.1Ce³⁺,0.2Mn²⁺ (x = 0–1) is achieved through the reduction of the distance between Ce³⁺ and Mn²⁺ ions in the dodecahedron. The above work provides support for the correct understanding of the luminescence behavior of Mn²⁺, and the influence of the microstructure on the energy transfer of Ce³⁺ → Mn²⁺ ions. Finally, high color rendering index (83.4) wLEDs were fabricated by the Lu_1.2Y_1.8Al_4.8Si_0.2O₁₂:0.1Ce³⁺,0.2Mn²⁺ phosphor and the blue chip under 120 mA.