钬镱铥掺杂C12A7单晶的制备及其上转换发光性能研究

发布时间：2018-07-17 02:30

【摘要】：七铝酸十二钙(C12A7)晶体是一种具备很好集成性能的新型功能材料,在固态多色激光器及3D显示等领域具有广阔的应用前景。本论文通过Ho~(3+),Yb~(3+)和Tm~(3+)离子按照一定摩尔比例进行掺杂,在C12A7单晶中成功实现上转换白光输出,并对上转换白光产生的机制进行了详细的分析。通过掺杂Mg~(2+)和Mn~(2+)离子分别对上转换白光的光强和色度进行了调节,实现了对C12A7单晶体系上转换白光性能的精细调节。采用高温固相法合成Ho~(3+)/Yb~(3+)/Tm~(3+)掺杂的C12A7多晶粉末,在980 nm激光激发下,样品在477 nm和652 nm处输出了对应于Tm~(3+)的1G4→3H6和1G4→3F4能级跃迁引起的上转换蓝光和红光;在550 nm处输出了对应于Ho~(3+)的5S2/5F4→5I8能级跃迁产生的上转换绿光,在665 nm处输出了对应于Ho~(3+)的5F5→5I8能级跃迁所引起的上转换红光。通过设计正交试验来研究Ho~(3+),Yb~(3+)和Tm~(3+)三种稀土离子浓度对C12A7多晶上转换发光性能的影响,并最终在C12A7多晶材料中实现白光输出。采用提拉法生长不同浓度Ho~(3+),Yb~(3+)和Tm~(3+)离子掺杂的C12A7单晶体,研究晶体生长过程中的各参数对晶体质量的影响。利用Crysmas软件模拟不同尺寸保温罩下的晶体生长温度场,并在模拟结果的基础上,测量实际晶体生长过程中的温度梯度来与模拟结果做对比,以保证建立最适合C12A7晶体生长的温度场(27℃/cm)。通过CGsim软件模拟不同转速下熔体的界面形状,寻找最合适的晶体生长速度和旋转速度(1mm/h和25 rpm)。研究了生长气氛对晶体质量的影响,发现随着氧气含量的增加,晶体中的铱杂质含量也随之增加,这也是晶体着色的原因。最终确定了完整的稀土掺杂C12A7晶体生长工艺,并生长出质量较好的C12A7单晶。通过XRD、紫外-可见吸收光谱和上转换发光光谱研究Ho~(3+),Yb~(3+)和Tm~(3+)离子浓度对C12A7晶体结构和上转换发光性能的影响。稀土离子所引起的晶格形状变化以及稀土离子之间能量传递作用的变化是影响上转换发光性能的主要因素。Ho~(3+)和Tm~(3+)离子浓度主要对输出光的色度有很好的调节作用,Yb~(3+)离子则主要改变上转换发光的光强。通过上转换功率曲线、发光能级寿命、中间态能级寿命测试以及稳态速率方程,分析了Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体中上转换白光的激发过程。在980 nm激光激发下,Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体产生的477 nm波长的蓝光为三光子连续能量传递过程,波长为550 nm的上转换绿光以及波长为652 nm和665 nm的上转换红光均为两光子连续能量传递过程。且上转换蓝光、绿光和红光的光子数排序为:蓝光绿光红光。研究了激发功率对Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体上转换白光性能的影响。随着激发功率的增加,上转换蓝光、绿光和红光光强均呈现逐渐增强的趋势,但增强幅度不同。上转换发光的色度逐渐由白光中心向蓝紫光交界区域偏移,这也是由于上转换蓝光的激发过程为三光子连续能量传递,而上转换绿光和红光的激发过程仅为两光子连续能量传递。研究了Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体中Tm~(3+)离子3F2,3和3H4能级的热耦合行为,获得了C12A7材料较高的光学温度探测灵敏度,比较适合用于温度探测,并且较高的灵敏度来源于较高的晶体结晶度。利用第一性原理计算了Yb~(3+)掺杂C12A7晶体的能带结构图和态密度图,并与未掺杂的理想C12A7晶体模型进行对比,发现稀土离子的掺入使得禁带宽度减小,但并没有改变费米能级位置。对C12A7与Yb~(3+)掺杂C12A7的结构进行分析,确定了稀土离子并没有进入C12A7晶体的笼状结构内部,而是以取代Ca~(2+)的形式存在。运用Judd-Ofelt理论计算了Ho~(3+)及Tm~(3+)掺杂C12A7材料的J-O强度参数以及光谱品质因子,计算结果表明稀土掺杂C12A7单晶材料是一种能够实现很好上转换发光的晶体材料。研究了金属离子Mg~(2+)和Mn~(2+)对Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体上转换白光性能的影响。Mg~(2+)离子的掺杂对Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体的上转换发光强度有很好的调节作用。Mg~(2+)离子的掺杂使得上转换发光过程中的中间态能级寿命增加,发光能级寿命降低,使得上转换过程所需光子数减少,宏观表现为上转换发光强度增强。Mn~(2+)离子的掺杂对Ho~(3+)/Yb~(3+)/Tm~(3+)/C12A7晶体的上转换白光色度有较好的调节作用。Mn~(2+)离子的掺杂会影响Ho~(3+)离子在5F5能级的粒子布居数,增加红光的发射几率,对上转换白光的色度有积极的调节作用。
[Abstract]:The seven calcium aluminate (C12A7) crystal is a new functional material with good integration properties. It has a broad application prospect in the fields of solid-state polychromatic laser and 3D display. In this paper, Ho~ (3+), Yb~ (3+) and Tm~ (3+) ions are doped in a certain molar ratio, and the upconversion white light output is successfully realized in the C12A7 single crystal. The mechanism of the upconversion white light was analyzed in detail. The light intensity and chromaticity of the upconversion white light were adjusted by doping Mg~ (2+) and Mn~ (2+) ions respectively. The fine regulation of the conversion of white light on the C12A7 single crystal system was realized. A high-temperature solid-phase method was used to synthesize the Ho~ (3+) /Yb~ (3+) /Tm~ (3+) doped C12A7 polycrystalline powder. Under the excitation of M laser, up conversion blue light and red light caused by 1G4 to 3H6 and 1G4 to 3F4 level transitions corresponding to Tm~ (3+) were output at 477 nm and 652 nm, and the upconversion green light corresponding to Ho~ (3+) transition was output at 550 nm. The effect of three rare earth ions concentration of Ho~ (3+), Yb~ (3+) and Tm~ (3+) on the performance of upconversion luminescence of C12A7 polycrystals was investigated by the orthogonal experiment, and the white light output was realized in the C12A7 polycrystalline material. The crystal of C12A7 with different concentration Ho~ (3+), Yb~ (3+) and ionic doping was studied by the drawing method. The influence of the parameters on the crystal quality during the growth process. Crysmas software is used to simulate the temperature field of the crystal growth under the different sizes of thermal insulation. On the basis of the simulation results, the temperature gradient in the actual crystal growth is measured to compare with the simulation results, so as to ensure the establishment of the temperature field (27 C /cm) suitable for the growth of C12A7 crystal. The interface shape of the melt at different rotational speeds was simulated by CGsim software to find the most suitable crystal growth speed and rotation speed (1mm/h and 25 RPM). The influence of the growth atmosphere on the crystal quality was studied. It was found that the iridium impurity content in the crystal increased with the increase of oxygen content, which was also the reason for the crystal coloring. Complete rare-earth doped C12A7 crystal growth process and high quality C12A7 single crystal have been grown. The effects of Ho~ (3+), Yb~ (3+) and Tm~ (3+) ion concentration on the crystal structure and upconversion luminescence properties of C12A7 are studied by XRD, UV Vis absorption and upconversion luminescence spectra. The lattice shape changes and rare earth ionization caused by rare earth ions are caused by rare earth ions. The change of energy transfer between the subgroups is the main factor affecting the performance of the upconversion luminescence. The concentration of.Ho~ (3+) and Tm~ (3+) ion mainly regulates the chromaticity of the output light, and the Yb~ (3+) ion mainly changes the light intensity of the upconversion luminescence. Through the upconversion power curve, the lifetime of the luminescent energy level, the lifetime test of the middle state and the stability of the light. The excited process of up conversion white light in the Ho~ (3+) /Yb~ (3+) /Tm~ (3+) /C12A7 crystal is analyzed by the state rate equation. The blue light of the Ho~ (3+) /Yb~ (3+) /Yb~ (3+) /Yb~ (3+) /Yb~ (3+) crystal is three photon continuous energy transfer process under the excitation of the 980 nm laser. The up conversion green light of the wave length of 550 and the up conversion red of the wavelength is 652 and 665. The light is two photon continuous energy transfer process. And up conversion blue light, the number of photons of green and red light is: blue and green light red light. The effect of excitation power on the performance of Ho~ (3+) /Yb~ (3+) /Tm~ (3+) /C12A7 crystal up conversion white light is studied. With the increase of the excitation power, the upconversion blue light, green light and red light intensity are gradually enhanced. Trend, but the enhancement range is different. The chromaticity of upconversion luminescence is gradually shifted from white light center to blue violet light junction area, which is due to the continuous energy transfer of three photons in the process of up conversion blue light, while the process of up conversion green light and red light is only two photon continuous energy transfer. The Ho~ (3+) /Yb~ (3+) /Tm~ (3+) /C12A7 crystal is studied. The thermal coupling behavior of the Tm~ (3+) ion 3F2,3 and 3H4 level in the body has obtained the higher sensitivity of the optical temperature detection of the C12A7 material, which is more suitable for the temperature detection, and the higher sensitivity is derived from the higher crystal crystallinity. The band structure diagram and the state density diagram of Yb~ (3+) doped C12A7 crystals are calculated by the first principle, and they are not used. The doping of the ideal C12A7 crystal model shows that the doping of rare earth ions reduces the band gap, but does not change the position of the Fermi level. The structure of the C12A7 and Yb~ (3+) doped C12A7 is analyzed, and the rare earth ions do not enter the cage like structure of the C12A7 crystal, but instead of the form of Ca~ (2+). The udd-Ofelt theory is used to calculate the J-O strength parameters and spectral quality factors of the Ho~ (3+) and Tm~ (3+) doped C12A7 materials. The calculation results show that the rare earth doped C12A7 single crystal material is a kind of crystal material which can achieve good upconversion luminescence. The conversion of white light on the crystal of metal ions Mg~ (2+) and Mn~ (2+) is studied. The doping of.Mg~ (2+) ion has a good regulating effect on the upconversion luminescence intensity of Ho~ (3+) /Yb~ (3+) /Tm~ (3+) /C12A7 crystal, the doping of.Mg~ (2+) ions makes the lifetime of the middle state of the middle state of the upconversion luminescence increases and the lifetime of the luminescent energy level decreases, which makes the number of photons in the upconversion process decrease and the macroscopic performance is the upturn. The doping of.Mn~ (2+) ion has a good regulating effect on the upconversion white light chromaticity of Ho~ (3+) /Yb~ (3+) /Tm~ (3+) /C12A7 crystal. The doping of.Mn~ (2+) ions will affect the number of particles in the energy level, increasing the emission probability of the red light, and has a positive effect on the chromaticity of the upconversion white light.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O734

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