Effect of Al/Si substitution on the structure and luminescence properties of CaSrSiO4:Ce3+ phosphors: analysis based on the polyhedra distortion

Blue-emitting CaSrSiO4: Ce3+, Li+ phosphors were prepared by a high temperature solid-state method, and the effect of substituting Al3+ for Si4+ in CaSrSiO4: Ce3+, Li+ has been studied. Crystal structures of the as-prepared Ca(1-y)Sr(1-y)Si(1-x)AlxO(4): yCe(3+), yLi(+) phosphors were resolved by the Rietveld method, which suggested that all the samples belonged to the orthorhombic symmetry (Pnma) group of alpha-CaSrSiO4. The photoluminescence (PL) emission and excitation spectra, the lifetime, and the effect of Al3+ concentration on the PL properties were investigated in detail. The emission peaks of the CaSrSi1-xAlxO4: Ce3+, Li+ (x = 0-0.10) phosphors were red-shifted from 452 to 472 nm with increasing Al/Si ratio. The red-shift of the Ce3+ emission is ascribed to the polyhedra distortion of the cations, originating from the variation in the neighboring [(Si,Al)O-4] polyhedra, and the detailed mechanism has been discussed.