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We have synthesized Ca 2 Si 5 N 8:Eu 2+ phosphor through a solid-state reaction and investigated its structural and luminescent properties.Our Rietveld refinement of the crystal structure of Ca 1.9 Eu 0.1 Si 5 N 8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions.Between 10 K and 300 K,Ca 2 Si 5 N 8:Eu 2+ phosphor shows a broad red emission band centred at ～1.97 eV-2.01 eV.The gravity centre of the excitation band is located at 3.0 eV-3.31 eV.The centroid shift of the 5d levels of Eu 2+ is determined to be ～1.17 eV,and the red-shift of the lowest absorption band to be ～ 0.54 eV due to the crystal field splitting.We have analysed the temperature dependence of PL by using a configuration coordinate model.The Huang-Rhys parameter S=6.0,the phonon energy ν=52 meV,and the Stokes shift S=0.57 eV are obtained.The emission intensity maximum occurring at ～200 K can be explained by a trapping effect.Both photoluminescence (PL) emission intensity and decay time decrease with temperature increasing beyond 200 K due to the non-radiative process.
We have synthesized Ca 2 Si 5 N 8: Eu 2+ phosphor through a solid-state reaction and investigated its structural and luminescent properties. Our Rietveld refinement of the crystal structure of Ca 1.9 Eu 0.1 Si 5 N 8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions. Bath temperature 10 K and 300 K, Ca 2 Si 5 N 8: Eu 2+ phosphor shows a broad red emission band center at ~ 1.97 eV-2.01 eV. The gravity center of the excitation band is located at 3.0 eV-3.31 eV. The centroid shift of the 5d levels of Eu 2+ is determined to be ~ 1.17 eV, and the red-shift of the lowest absorption band to be ~ 0.54 eV due to the crystal field splitting. We have analysed the temperature dependence of PL by using a configuration coordinate model. The Huang-Rhys parameter S = 6.0, the phonon energy ν = 52 meV, and the Stokes shift S = 0.57 eV are obtained. The emission intensity maximum occurring at ~ 200 K can be explained by a trapping effect.Both photoluminescence (PL) emission intensity and d ecay time decrease with temperature increasing beyond 200 K due to the non-radiative process.