Synthesis and luminescence properties of novel red phosphors LiRGe2O6:Mn4+ (R = Al or Ga)

LiRGe 2 O 6 :xMn 4+ (R = Al or Ga) (0 ≤ x ≤ 1.0 mol%) phosphors are synthesized by solid-state reaction method in air, and their crystal structures, luminescence properties, and fluorescence lifetimes are investigated. Their photoluminescence (PL) bands peaking at ∼ 670 nm owing to the 2 E →  4 A 2 transition of Mn 4+ ion cover the region from 620 to 750 nm (λex = 289 nm), and photoluminescence excitation (PLE) bands (λem ≈ 670 nm) are observed in the range of 200–550 nm. With excitation 289 nm, PL intensity of LiAlGe 2 O 6 :0.6%Mn 4+ phosphor is far stronger than that of LiGaGe 2 O 6 :0.6%Mn 4+ phosphor owing to the influence of crystal field. The optimal Mn 4+ ions concentration is ∼0.6 mol%. The fluorescence lifetime and quantum efficiency of LiAlGe 2 O 6 :0.6%Mn 4+ and LiGaGe 2 O 6 :0.6%Mn 4+ phosphors are ∼1.55 ms, 68.5 μs, 32%, and 15%, respectively. Luminous mechanism, the temperature quenching mechanism, and the influence of crystal field to luminous properties are analyzed and discussed, respectively. The experiment results are helpful to develop other novel Mn 4+ -doped phosphors.