Synthesis of nitridosilicate CaSr1-x Eux Si5 N8 (x=0-1) phosphor by calcium cyanamide reduction for white light-emitting diode applications

A convenient calcium cyanamide (CaCN2) reduction route was developed to synthesize the Eu2+ -doped nitridosilicate phosphors, CaSr1-x Eux Si5 N8 (x=0-1), and the photoluminescence properties of the obtained phosphors were characterized for solid-state lighting applications [white light-emitting diodes (LEDs)]. The Rietveld refinement analysis for undoped CaSrSi5 N8 was carried out in space group Pmn 21 (no. 31) with a=569.0(4) pm, b=673.0(1) pm, and c=932.0(6) pm. The Eu2+ ions formed a complete solid solution by occupying the Sr2+ sites in CaSrSi5 N8 host lattice. A typical sample doped with an optimized amount of Eu2+ (2 atom % vs CaSr) showed a broadband absorption covering the range from UV to visible region (380-500 nm) and strong red emission peaking at 629 nm, revealing that this phosphor was a potential candidate for the phosphor-converted white LEDs. Under excitation of 460 nm, this phosphor gave the intensity comparable (about 120%) to that of yttrium aluminum garnet YAG: Ce3+ (P46-Y3) standard. The emission peaks of CaSr1-x Eux Si5 N8: Eu2+ varied from 625 to 680 nm with increasing Eu2+ ion concentration. The redshifting behavior of the emission band dominantly contributed to the energy migration among Eu2+ ions.