Crystal Chemistry and Luminescence of Ce³⁺-Doped Lu₂CaMg₂(Si,Ge)₃O₁₂ and Its Use in LED Based Lighting

Abstract

In this paper, we describe the formation and luminescence of a new garnet phosphor for light emitting diode (LED) based lighting, Lu2CaMg2(Si,Ge)3O12:Ce3+. The regions for garnet phase formation are initially described with respect to larger rare earth substitution and show reasonable correlation to previous crystal chemistry studies for the garnet parent structure. While the pure silicate phosphor also has apatite second phases, a significant amount of Ce3+ enters the garnet phase, giving Ce3+ luminescence that is significantly redder when compared to typical Al3+ garnet phosphors with quantum efficiencies comparable to commercial Ce3+ garnet phosphors. Potential reasons for the emission red shift and the high quantum efficiency are discussed. Finally, the performance of these new phosphors is tested within LED based lamps. Lamps using these phosphors can reach color temperatures required for general illumination lighting and also have comparable phosphor conversion efficiencies when compared to lamps using typical garnet phosphors.