所報 104

31/38

－　　－29Published PaperLuminescence enhancement of LiSrPO4:Eu2+ phosphor by Mg2+ ion additionShinnosuke KAMEI, Tomoki HATSUMORI, Takuya HASEGAWA, Tadashi ISHIGAKI, Kazuyoshi UEMATSU, Kenji TODA, Mineo SATOThis paper describes a new method of the luminescence enhancement s of blue-emitting phosphate phosphors. Mg-doped LiSrPO4:Eu2+ (Li(Sr, Mg)PO4:Eu2+) phosphors, in which some Sr2+ ions were replaced by Mg2+ ions, were prepared using a conventional solid-state reaction method. The crystal structure of the phosphors was hexagonal, which is the high-temperature phase of LiSrPO4, even though synthesis was carried out at a relatively low temperature of 900 ℃. Fluorescence could be efficiently excited in the 220–400 nm ultraviolet regions, and bright blue emission was produced with a peak at 448 nm. The emission intensity was higher than that for LiSrPO4:Eu2+ without Mg doping, and a lower Eu content (1 mol%) was required in order to reach the maximum intensity. These results indicate that the blue emitting Li(Sr, Mg)PO4:Eu2+ phosphor is a promising candidate for phosphor-conversion white Light Emitting Diodes.Keywords: Optical materials, inorganic compounds, chemical synthesis, phosphorsMg2+イオン添加によるLiSrPO4:Eu2+蛍光体の発光強度向上　本研究は，リン酸塩化合物の青色発光蛍光体であるLiSrPO4:Eu2+蛍光体のさらなる発光強度向上を目指した．LiSrPO4は一般的な固相反応で簡便に合成でき，600～1000度の合成温度では低温相（斜方晶または単斜晶）となり，1000度以上の合成温度では高温相（六方晶）の結晶構造をとる．MgイオンをSrイオンサイトに一部固溶させることにより，900度の合成温度で高温相である六方晶の合成が行えることを見出した．この高温相となるLi(Sr, Mg)PO4に発光イオンとしてEu2+イオンを固溶させたLi(Sr, Mg)PO4:Eu2+蛍光体の蛍光特性は，Mgイオン無置換の高温相のLiSrPO4:Eu2+蛍光体と比較して，発光強度が向上することが確認された．すなわち，Mgイオンを添加させることにより，LiSrPO4蛍光体は低い合成温度で高発光強度を示す青色蛍光体を作製できることを見出した．キーワード：光学材料，無機化合物，化学合成，蛍光体Journal（掲載誌）Materials Research Innovations Vol. 23, Issue 6, 359-362, Jul 2019Taylor & Francis Online: www.tandfonline.com