新穎紫外光稀土螢光體之製備及發光特性之研究

Abstract

隨環保意識的逐漸提升，為迎接綠色環保時代的來臨，本研究主旨為合成及開發可被真空紫外光所激發之新穎放射紫外光(波長200-400 nm)螢光體，並探討其發光相關原理與機制，以評估螢光體在紫外線殺菌或光療元件之應用潛力。本論文所探討之重點材料為可供準分子氙氣放電燈激發之含磷酸鹽、硼酸鹽及矽酸鹽為主體之紫外光放射螢光材料。 本研究主要利用國家同步輻射研究中心所提供真空紫外光源進行螢光體之發光特性量測，同時亦利用X-光繞射與電子顯微鏡術進行螢光材料晶相與微結構鑑定分析。本研究分別探討了發射UVB波段的NaCa(Y,Gd)(PO4)2、Na2(Y,Gd)2O(BO3)2、Li6(Y,Gd)(BO3)3、Na(Y,Gd)Si2O6、NaCa(Y,Pr,Gd)(PO4)2、Li6(Y,Pr,Gd)(BO3)3及Na(Y,Pr,Gd)Si2O6與發射UVC波段的NaCa(Y,Pr)(PO4)2與Na(Y,Pr)Si2O6等兩系列螢光體。 當以172 nm波長激發NaCa(Y,Gd)(PO4)2、Na2(Y,Gd)2O(BO3)2、Li6(Y,Gd)(BO3)3、Na(Y,Gd)Si2O6、NaCa(Y,Pr,Gd)(PO4)2、Li6(Y,Pr,Gd) (BO3)3及Na(Y,Pr,Gd)Si2O6時，可發現源自於4f 7→ 4f 7躍遷且波長為313 nm的Gd3+ UVB發光；而NaCa(Y,Pr)(PO4)2與Na(Y,Pr)Si2O6在相同激發條件下，則可發現源自於Pr3+ 4f 15d1→4f 2躍遷之UVC發光。此外，在Pr3+與Gd3+共摻螢光體中，Pr3+可作為將能量傳遞至活化劑Gd3+的敏化劑，在相同激發條件下，本研究發現NaCa(Y,Pr,Gd) (PO4)2、Li6(Y,Pr,Gd)(BO3)3與 Na(Y,Pr,Gd)Si2O6的紫外光放射強度分別為飛利浦LaB3O6:Bi3+,Gd3+商品的1.6、5.4及1.4倍，預期上述螢光體具有應用於殺菌或光療之潛力。

With the gradual enhancement of environmental awareness, the development of green luminescent materials has been an important issue in phosphors research. This research is attempted to synthesize and investigate new UV-emitting materials, which can be excitated by 172 nm and used for the applications of phototherapy, sterilization, and disinfection. We have explored and investigated the luminescence mechanism of four series of UV-emitting phosphors, including nine types of rare earth-doped phosphates, silicates and borates. In this study, using the vacuum ultraviolet (VUV) light source provided by National Synchrotron Radiation Research Center (NSRRC), as well as the X-ray diffraction technique and electron microscopy analysis, we have prepared and investigated UVB-emitting NaCa(Y,Gd) (PO4)2, Na2(Y,Gd)2O(BO3)2, Li6(Y,Gd)(BO3)3, Na(Y,Gd)Si2O6, NaCa (Y,Pr,Gd)(PO4)2, Li6(Y,Pr,Gd)(BO3)3 and Na(Y,Pr,Gd)Si2O6; UVC- emitting NaCa(Y,Pr)(PO4)2 and Na(Y,Pr)Si2O6. Under excitation at 172 nm, the NaCa(Y,Gd)(PO4)2, Na2(Y,Gd)2O(BO3)2, Li6(Y,Gd)(BO3)3, Na(Y,Gd)Si2O6, NaCa(Y,Pr,Gd) (PO4)2, Li6(Y,Pr,Gd)(BO3)3 and Na(Y,Pr,Gd)Si2O6 phosphors were found to give sharp UVB emission centered at 313 nm, which was attributed to the 4f7→4f7 transition of Gd3+. Under the same excitation, NaCa(Y,Pr)(PO4)2 and Na(Y,Pr)Si2O6 were found to emit UVC light, which was found to be due to the 4f15d1 →4f 2 transition of Pr3+. With the co-doping of Pr3+ as a sensitizer, NaCa(Y,Pr,Gd)(PO4)2, Li6(Y,Pr,Gd)(BO3)3, and Na(Y,Pr,Gd) Si2O6 exhibit a much stronger emission at 313 nm. The emission intensity of the UVB-emitting NaCa(Y0.8293Pr0.0007Gd0.17)(PO4)2, Li6(Y0.695Pr0.005 Gd0.3)(BO3)3 and Na(Y0.775Pr0.005 Gd0.22)Si2O6 was found to be 1.6, 5.4, and 1.4 times that of the UVB emission of the patented LaB3O6:Bi3+,Gd3+ commodity, respectively. Our investigation results indicate that the above three Pr3+/Gd3+-coactivated phosphors may have great potential for practical application in phototherapy and tanning. The luminescence performance of all types of UV radiation was found to be crucially dependent on the chemical compositions, bonding and crystal structure of the host matrix.