磁鉛礦型鹼土鋁鎵酸鹽螢光體之合成與特性鑑定

Abstract

本研究主要探討具有磁鉛礦結構而化學式為AB12O19 (A , B分別為+2 , +3價陽離子) 的主體分別摻雜稀土與過渡金屬陽離子之Sr(Ga1-xAlx)12O19:R系列螢光體主體組成、活化劑離子濃度、晶體結構與溫度等因素對上述螢光體發光性質的效應。 Sr(Ga1-xAlx)12O19:R ( 0 ≦x≦1.0 ; R= Eu3+ , Tb3+ , Cr3+ , Mn2+)系列螢光體係利用固態燒結法於1,400℃空氣中(R為Mn2+之樣品須再於1,000℃以氫/氬氣還原)方能製得。 X光繞射圖譜分析顯示：Sr(Ga1-xAlx)12O19:R主體晶格尺寸隨Al3+取代量增加而縮減，此亦導致主體能隙隨之遞增 。 陰極射線發光光譜顯示SrGa12O19呈現主體自身活化且放射波長為429 nm之發射峰 ; 而SrAl12O19則否。 此外，紫外光致發光光譜研究顯示： 隨 主 體 晶 格 尺 寸 縮 小， Sr(Ga1-xAlx)12O19: Cr3+系列螢光體2E →4A2放射峰波長產生藍位移，而Sr(Ga1-xAlx)12O19: Mn2+系列螢光體4T1→6A1放射峰波長則產生紅位移。反之，Sr(Ga1-xAlx)12O19: Eu3+或Tb3+系列螢光體發射峰波長則不受主體晶格尺寸的影響。 另一方面，我們也探討了活化劑離子濃度對SrM12O19: Eu3+或Tb3+ ( M = Al , Ga ) 發光強度的效應。並發現最佳Eu3+與Tb3+離子濃度分別為10 atom % 與3 atom %。SrM12O19: Cr3+ ( M = Al , Ga ) 與SrGa12O19: Mn2+三螢光體之溫度對發射光譜效應之研究顯示：前者中Cr3+離子之R lines 群所對應λem為692.6 , 694.2 nm，而後者Mn2+離子4T1→6A1躍遷所對應λem為503 nm ﹔而放射峰強度，則隨溫度降低而呈現增強的現象。 本研究也對MgGa2O4:M ( M = Eu3+ , Tb3+ , Mn2+ )系列螢光體之光致發光與陰極射線發光光譜深入探討。

This research is attempted to investigate the effect of host compositions, activator concentration, crystal structure, and temperature on the luminescent properties of magnetoplumbite-type Sr(Ga1-xAlx)12O19: R ( R = Eu3+ , Tb3+ , Cr3+ , Mn2+ ; 0 ≦x≦1.0) ( SGAO:R ) phosphors. The SGAO:R phases with R = Eu3+ , Tb3+ , Cr3+ , Mn2+ ) were prepared at 1,400℃ in the air via solid-state route, whereas the formation of SGAO:Mn2+ requires additional annealing under H2/Ar atmosphere at 1,000℃. The lattice dimensions of Sr(Ga1-xAlx)12O19: R were found to shrink gradually with increasing content of Al3+ dopant, as indicated by X-ray diffraction analysis. In addition, SrGa12O19 was found to be self-activating with emission wavelength (λem) of 429 nm, whereas SrAl12O19 is not, as indicated by cathodoluminescence (CL) measurements. On the other hand, with shrunk lattice dimensions the λem corresponding to 2E →4A2 transition in Sr(Ga1-xAlx)12O19:Cr3+ exhibited blue shift, whereas that corresponding to 4T1→6A1 transition in Sr(Ga1-xAlx)12O19:Mn2+ exhibited red shift. These observation can be rationalized by Tanabe-Sugano diagrams for octahedral Mn2+ and Cr3+ ions , respectively. On the contrary, theλem attributed to Sr(Ga1-xAlx)12O19:Eu3+ or Tb3+ phosphors remains unchanged with expanded lattice dimensions. Furthermore, we have also investigated the effect of activator concentration on the luminescent properties of SrM12O19:Eu3+ or Tb3+ ( M = Al, Ga ) and the optimal concentration was found to be 10 and 3 atom % for phases with Eu3+ and Tb3+ dopants, respectively. Theλem of typical R-lines of Cr3+ in SrM12O19: ( M = Al, Ga) has been determined to be 692.6 and 694.2 nm, respectively, and that attributed to 4T1→6A1 transition observed in SrGa12O19: Mn2+ was found to be 503 nm and highly dependent on the temperature, as indicated by temperature dependent photoluminescence (PL) emission studies. The PL and CL emission spectra of MgGa2O4: M ( M = Eu3+ , Tb3+ , Mn2+ ) phases were also investigated in this research.