【作者】 刘春光；

【导师】 刘玉学；

【作者基本信息】 东北师范大学 ， 凝聚态物理， 2013， 博士

【摘要】 电子俘获材料在红外探测、红外上转换、探测计量、光计算、光信息处理、光存储、及X射线影像存储等领域都具有广阔的应用前景。本文以12CaO·7Al₂O₃（C12A7）为基质材料，采用化学共沉淀方法制备了C12A7：Eu²⁺、C12A7：Eu²⁺,Dy³⁺和C12A7：Eu²⁺,Nd³⁺等电子俘获材料，并通过X射线衍射（XRD）、激发光谱、发射光谱、余辉衰减、光激励发光（PSL）和热释发光等测试手段系统研究了C12A7:Eu²⁺,Dy³⁺和C12A7:Eu²⁺,Nd³⁺的微结构和光学性质，探讨了电子俘获材料的光存储机制，并研究了C12A7:Eu²⁺,Dy³⁺的X射线存储特性，得到了较清晰的X射线存储图像。C12A7：Eu²⁺,Dy³⁺的测试结果表明，C12A7:Eu²⁺,Dy³⁺的激发峰位置分别位于254nm和325nm，发射峰位于444nm，为Eu²⁺的4f65d到4f7的发射，激发光谱和发射光谱均显示为宽峰线形。蓝色余辉时间较长，说明C12A7:Eu²⁺,Dy³⁺中存在许多较浅陷阱。根据热释发光得到两个深陷阱的激活能分别为0.81eV和0.95eV。C12A7:Eu²⁺,Dy³⁺样品经紫外光辐照后，用980nm或808nm红外光激励后有较强的光激励发光。研究比较了C12A7:Eu²⁺和C12A7：Eu²⁺,Nd³⁺的光学特性， C12A7:Eu²⁺的激发光谱中可以明显地观察到两个归属于Eu²⁺4f-5d激发峰，分别位为260nm和315nm，而C12A7:Eu²⁺,Nd³⁺只有一个较强激发峰，位于315nm，260nm位置激发峰值很弱。紫外线照射后，可观察到蓝色长余辉发光现象。余辉衰减曲线由快过程和慢过程组成，余辉时间比C12A7:Eu²⁺,Dy³⁺长，根据热释发光曲线得到C12A7:Eu²⁺,Nd³⁺深陷阱的激活能是0.74eV，有较强的光激励发光（PSL）。根据材料的光学特性研究了稀土离子掺杂C12A7基电子俘获材料的陷阱特性和光存储机理，实验研究了C12A7:Eu²⁺,Dy³⁺X射线存储特性，通过实验我们发现，C12A7:Eu²⁺,Dy³⁺经在空气中1380℃烧结10小时处理后光学性质发生了显著变化，X射线影像存储效果较好，其激发光谱为250到470nm的宽带吸收，主要激发峰位置分别位于330，349、362、385nm等，发射光谱显示主要来自Eu²⁺和Dy³⁺的光发射，发射峰位440，480和572nm，分别归属为Eu²⁺的5d→4f跃迁发射和Dy³⁺的⁴F_9/2→⁶H_15/2和⁴F_9/2→⁶H_13/2的发射。在发射谱中没有观察到Eu²⁺到Dy³⁺的能量传递，说明空气中热处理下使掺入的Dy³⁺从还原气氛处理条件下的陷阱中心转变成为了发光激活中心。经空气高温烧结样品的余辉时间变短，说明该样品中的浅陷阱数量减少。样品经紫外光辐照后，用980或808nm红外光激励后有较强的光激励发光。利用该样品我们得到了较为清晰的X射线存储图像，同时探讨了降低X射线辐照剂量和提高X射线影像空间分辨率的方法和途径。我们的研究结果表明C12A7材料是一种理想的稀土离子掺杂的基质材料，在应急照明、光信息存储及X射线影像存储等领域有着广阔的应用前景。更多还原

【Abstract】 Electron trapping materials have wide application prospects in many fields, such asinfrared detection, infrared upconvertion imaging, optical storage, detectionmeasurement, optical computing, optical information processing and X ray storageimaging, etc.In this dissertation, rare earth ions doped12CaO·7Al₂O₃（C12A7） electron trappingmaterials, like C12A7:Eu²⁺,C12A7:Eu²⁺,Dy³⁺and C12A7:Eu²⁺, Nd³⁺were prepared bychemical coprecipitation method.X ray diffraction （XRD）, excitation and emissionspectra, afterglow decaying measurent,optical stimulated luminescence （PSL） andthermoluminescence （TL） techniques were used to characterize their microstructuresand optical properties. The optical storage mechanisms of these electron trappingmaterials were discussed and the X-ray storage characteristics of C12A7:Eu²⁺,Dy³⁺were studied. The clear X-ray storage graph was obtained.The experimental results showed that C12A7:Eu²⁺,Dy³⁺exhibited similar two broadexcitation peaks, respectively, located at254and325nm and the same wide emissionpeak at444nm, which is attributed to Eu²⁺emission between4f65d1to4f7. After325nm UV irradiation, when stimulated with980or808nm infrared light, the long lastingafterglow with blue emission was obtained.By using TL, we can observe the shallow（0.81eV） and deep traps （0.95eV） in C12A7:Eu²⁺,Dy³⁺.Comparing the excitation spectrum of C12A7:Eu²⁺with that of C12A7:Eu²⁺,Nd³⁺,two intense peaks of C12A7:Eu²⁺, respectively, at260and315nm can be observed, butthere is only one strong peak located at315nm and a weaker peak at260nm inC12A7:Eu²⁺,Nd³⁺can be seen. The above results indicated that the Nd³⁺dopping mighthave caused the change in the crystal field and the symmetry of Eu²⁺in C12A7. Afterultraviolet radiation, a blue luminescence phenomenon of long afterglow can be seen inthe dark environment. The afterglow decay curve was composed of a fast-and a slowprocess and the afterglow decay time was longer than that of C12A7:Eu²⁺,Dy³⁺. Theactivation energy of deep traps in C12A7:Eu²⁺,Nd³⁺was ascertained to be0.74eV byTL curve.By using PL, PSL and TL, the trap characteristics and optical storage mechanismof rare earth ions doped C12A7electron trapping materials trap were studied. Especially,X-ray storage characteristics of C12A7:Eu²⁺,Dy³⁺samples was discussed in details. When we burnt them at1380℃for10hours, their optical properties exhibited obviouschanges and excellent X-ray storage imaging was achieved.Their excitation spectrashowed s broadband excitation peaks in the range from250to470nm, located at349,362,385nm etc. For the emission spectra of the air treated samples, the emission peakswere detected at480and572nm, respectively, belonged to the transitions of⁴F_9/2→⁶H_15/2and⁴F_9/2→⁶H_13/2of Dy³⁺under UV excitation. No energy transfer fromEu²⁺to Dy³⁺was observed.These results indicated that the heat-treatment in air havecaused the transformation of doped Dy³⁺in C12A7from the traps into activatin centers.The afterglow of the air treated samples became short suggesting that the amount ofdeep traps decreased. After irradiated by UV, these samples exhibited strongphoto-stimulable luminescence when stimulated with980or808nm infrared light. Wehave obtained the clearer X-ray storage images of the air treated sample than that of thereduced sample. We also tried to find new ways to reduce the X-ray irradiation dose andto improve the X-ray imaging space resolution.Our research showed that C12A7material is a kind of ideal matrix materials dopedwith rare earth ions, which has a wide application prospect in the field of emergencylighting, optical information storage and X-ray storage image etc.更多还原