Highly efficient cyan-emitting garnet Ca3Hf2SiAl2O12: xCe3+ phosphor for solid state white lighting

Abstract

In this paper, we have synthesized a new garnet structure compound Ca₃Hf₂SiAl₂O₁₂ and a series of Ce³⁺-doped Ca₃Hf₂SiAl₂O₁₂: xCe³⁺ phosphors. The crystal structure and luminescence properties of the Ca₃Hf₂SiAl₂O₁₂: xCe³⁺ are investigated in detail. Transmission electron microscopy analysis and XRD Rietveld refinement shows that Ca₃Hf₂SiAl₂O₁₂ is body-centered cubic and belongs to Iad (230) space-group with a = 12.3666 Å. Ca₃Hf₂SiAl₂O₁₂: xCe³⁺ has broad excitation bands at 330 and 400 nm attributed to the characteristic Ce³⁺ 5d–4f transition and can produce cyan emission under 400 nm UV light excitation. The emission intensity of CHSA: 1%Ce³⁺ phosphor can reach 68.9% of YAG: Ce³⁺ (commercial) and 72.1% of Ca₈Mg(SiO₄)₄Cl₂: Eu²⁺ (commercial). The average decay lifetime of Ca₃Hf₂SiAl₂O₁₂: 1%Ce³⁺ is 48.91 ns, which is consistent with the nanosecond peculiarity of Ce³⁺. In the process of increasing the temperature from 25 °C to 250 °C, the integrated emission intensity of Ca₃Hf₂SiAl₂O₁₂: 0.5%Ce³⁺ only decreases to 57.8% (250 °C) and shows nice thermal stability compared with commercial YAG: Ce³⁺(P46-Y3). Furthermore, Ca₃Hf₂SiAl₂O₁₂: 0.5%Ce³⁺ exhibits outstanding quantum efficiency (74.7%). It reveals that Ca₃Hf₂SiAl₂O₁₂: xCe³⁺ possesses remarkable optical properties and can be utilized in UV-LEDs.