Chin. Phys. B., 2009,18, 8, 3555. https://iopscience.iop.org/article/10.1088/1674-1056/18/8/070

We have synthesized Ca₂Si₅N₈:Eu²⁺ phosphor through a solid-state reaction and investigated its structural and luminescent properties. Our Rietveld refinement of the crystal structure of Ca_1.9Eu_0.1Si₅N₈ reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions. Between 10 K and 300 K, Ca₂Si₅N₈:Eu²⁺ 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 Eu²⁺ 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 hv = 52 m eV, and the Stokes shift ΔS = 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.