【作者】 孟丹；

【导师】 刘玉学；

【作者基本信息】 东北师范大学 ， 凝聚态物理， 2021， 硕士

【摘要】 近年来,X射线荧光粉在医学成像、工业无损检测、安检等领域显示了重要的应用前景。其中,基于X射线荧光粉的数字化X射线成像技术（DR）,具有成像质量好、检测效率高、易于保存等优点,日益受到人们的重视。目前,基于稀土离子掺杂的传统X射线荧光粉具有掺杂浓度低、效率低、响应时间长以及与CCD图像传感器的灵敏波长匹配不佳等问题,DR成像的质量还需进一步提高。而自激活类荧光粉（如钒酸盐等）具有高浓度的发光中心,并具有与CCD传感器相匹配的发射波长等优点。因此,探索制备新型高效的钒酸盐基X射线纳米荧光粉具有重要的实际意义和应用价值。本文采用化学共沉淀法制备了Zn₃（VO₄）₂纳米荧光粉和不同Ba²⁺掺杂浓度的Zn_3-xBa_x（VO₄）₂纳米荧光粉。利用X射线衍射、扫描电子显微镜成像、激发和发射光谱等技术手段,较系统地研究了其微结构和光学特性,并探索了其X射线成像的应用。具体的实验结果如下:1.采用化学共沉淀方法（溶液PH值为6）结合500℃煅烧2小时的条件下制备获得了Zn₃（VO₄）₂纯相粉末样品。通过优化制备条件,得到了尺寸均匀,分散性好的球形纳米粒子,其平均粒径约为67 nm。2.在325 nm的激发下,Zn₃（VO₄）₂纳米粉末在400-800 nm范围呈现一个强宽带发射,其峰值位于550 nm。其中,位于538 nm和604 nm的两个发射峰,可归属于来源于VO₄^3-的³T₂→¹A₁和³T₁→¹A₁的跃迁。监测550 nm的发射,在200-400 nm范围,Zn₃（VO₄）₂纳米荧光粉呈现宽吸收带。位于273 nm和335 nm处的两个激发峰,分别对应于VO₄^3-的¹A₁→¹T₂和¹A₁→¹T₁的跃迁。Zn₃（VO₄）₂纳米荧光粉在X射线激发下的发射光谱呈现主峰为570 nm的宽带发射,与CCD传感器灵敏波长匹配较好。尤其,其在X射线激发下不仅没有余辉,而且荧光寿命短（响应快）。3.采用化学共沉淀方法结合后期热处理的手段制备了具有不同Ba²⁺掺杂浓度的Zn_3-xBa_x（VO₄）₂纳米粉末。在0.0075-0.045的Ba²⁺离子掺杂浓度范围内,用325 nm光激发下,该样品位于550 nm处宽带发射峰的发光强度随浓度增加呈现先增强后不变的趋势。当Ba²⁺离子掺杂浓度为x=0.0375,发光强度最大。在紫外光（325 nm）和X射线激发下,最优掺杂浓度的Zn_3-xBa_x（VO₄）₂（x=0.0375）纳米荧光粉与Zn₃（VO₄）₂纳米荧光粉相比,位于550 nm处宽带发射峰光发射强度均提高了三倍左右。其发光增强可归因于大原子序数的Ba²⁺离子取代Zn²⁺离子后,[VO₄]四面体产生更大程度的畸变,且对X射线的吸收能力进一步增强造成的。最后,将Zn_2.9625Ba_0.0375（VO₄）₂纳米荧光粉制成了薄膜成像版,实现了X射线成像应用。更多还原

【Abstract】 In recent years,X-ray phosphors have shown important applications,such as medical imaging,industrial nondestructive testing and security inspection.Among them,digital X-ray imaging（DR）technology using X-ray phosphor has attracted more attention due to its high-quality imaging,high detection efficiency and easy preservation.At present,because traditional X-ray phosphors like rare earth ion doped phosphos have exhibited some shortcomings,such as low doping concentration,low efficiency,long response time and poor matching with the sensitive wavelength of CCD image sensor,the quality of DR imaging is required to further be improved.Meanwhile,self-activated phosphors（such as vanadate）have some advantages like high concentration of emission center and emission wavelength matched with CCD sensor.Therefore,it is essential to prepare efficient vanadate-based X-ray nanophosphors.In this dissertation,Zn₃（VO₄）₂ and Zn_3-xBa_x（VO₄）₂ nanophosphors with different Ba²⁺doping concentrations were prepared by a chemical co-precipitation method.Their microstructure and optical properties were studied by X-ray diffraction,scanning electron microscope imaging,excitation and emission spectra and X-ray imaging using Zn_3-xBa_x（VO₄）₂nanophosphors was realized.The detailed experimental results are given as follows:1.Single-phased Zn₃（VO₄）₂ powders were prepared by a chemical co-precipitation method（solution p H value=6）and following a calcination at 500℃for 2 h.The spherical nanoparticles with uniform size and good dispersion were obtained through optimizing the preparation coditions and the averaged particle size was found to be about 67 nm.2.For Zn₃（VO₄）₂ nanopowders under 325 nm excitation,in the 400-800 nm region,a strong broadband emission peak at 550 nm can be observed.This peak can be divided into two emission peaks at 538 and 604 nm,originating from the ³T₂→¹A₁ and ³T₁→¹A₁transitions of VO₄^3-.When monitoring 550 nm emission,in the 200-400 nm range,Zn₃（VO₄）₂nanophophors exhibited a wide absorption band.This band can be divided into two excitation peaks at 273 and 335 nm,corresponding to the ¹A₁→¹T₂ and ¹A₁→¹T₁ transitions of VO₄^3-,respectively.Under X-ray excitation,Zn₃（VO₄）₂ nanophophors showed a broadband emission peaks at 570 nm,which is well matched with the sensitive wavelength of CCD sensor.In particular,under X-ray excitation,no afterglow can be detected and the short fluorescent lifetime（fast response）can be obtained.3.Zn_3-xBa_x（VO₄）₂powders with different Ba²⁺doping concentrations were prepared by a chemical co-precipitation combined with post-heat treatment.Under 325 nm excitation,in the doping concentration range of 0.0075-0.045,their emission intensity at 550 nm exhibited a first increasing and then unchanged trend with increasing Ba²⁺doping concentration.As the doping concentration was x=0.0375,the strongest luminescent intensity can be obtained.Compared with Zn₃（VO₄）₂ nanophosphors,the emission intensity of Zn_3-xBa_x（VO₄）₂nanophosphors（x=0.0375）increased by about three times under ultraviolet light（325 nm）and X-ray excitations.The enhanced luminescence can be attributed to the larger distortion of[VO₄]tetrahedron and increased X-ray absorption capacity after the replacement of Zn²⁺ions by Ba²⁺ions with larger atomic number.Finally,Zn_2.9625Ba_0.0375（VO₄）₂ nanophosphors were used to fabricate imaging plate in a form of thin film and X-ray imaging was realized.更多还原