Structure and Photoluminescence Properties of MIIMIIISi4N7: Eu2+ (MII = Ca, Sr, Ba/MIII = Y, La) Phosphors Prepared by Carbothermal Reduction and Nitridation

New nitride compound phosphors of (MMSi4N7)-M-II-Si-III: Eu2+ (M-II = Ca, Sr, Ba /M-III = Sc, La) with the same composition as SrYSi4N7:Eu2+ were successfully synthesized from (MCO3)-C-II, (M2O3)-O-III, Eu2O3, and Si3N4 raw materials using carbon powder as a reductant by optimizing the synthesis conditions such as carbon amount and heating temperature as follows: amount of carbon; 66-90 at% to stoichiometric ratio, heating condition; 1000 degrees C for 2 h followed by 1550 degrees C for 6 h in flowing N-2 atmosphere. From the structural analysis including Rietveld refinement, the crystal structure of (MScSi4N7)-Sc-II host lattices were the same as SrYSi4N7 and crystallized in a hexagonal symmetry (P6(3)mc), whereas SrLaSi4N7:Eu2+ crystallized in an orthorhombic one (Pmmm). The resultant (MScSi4N7)-Sc-II:Eu2+ and SrYSi4N7:Eu2+ phosphors were effectively excited by near-UV light (390 nm) and showed green and yellow emission, respectively, suggesting that these compounds are noted as one of the light components to fabricate white LED by combining with near-UV LEDs. The optimal Eu2+ concentration for SrScSi4N7:Eu2+ was 4 at% and the thermal stability of this sample was comparable to commercially available Y3Al5O12:Ce3+ yellow phosphor. (C) 2012 The Electrochemical Society.