Synthesis and luminescent characterization of Sr2SiO4:Eu2+ nanopowders

Sr2SiO4:Eu2+ nanopowders were synthesized by a co-precipitation method using strontium nitrate, 3-aminopropyltriethoxysilane (APTES), europium nitrate hydrate, and a flux (NH4Cl). The structural and luminescent properties strongly depended on the firing conditions, the amount of APTES, and the flux content. Alpha'-Sr2SiO4 was produced as a dominant phase after firing as-prepared powders without a flux, whereas the addition of NH4Cl caused beta-Sr2SiO4 to be the primary phase. At a small amount of APTES, the as-prepared powders that were fired with NH4Cl consisted of the beta-Sr2SiO4, Sr3SiO5, and un-reacted SrO phases. Then, the phase transformation from SrO and Sr3SiO5 to beta-Sr2SiO4 gradually proceeded as the amount of APTES was increased, leading to the pure beta-Sr2SiO4 phase at 0.5 M APTES. The phase transition and photoluminescence properties strongly relied on the amount of NH4Cl. The preparation condition of 0.5 M APTES and 2 wt% NH4Cl was the optimum condition to obtain the pure beta-Sr2SiO4:Eu2+ phase and the most excellent PL intensity.