Growth and spectra properties of Ce~(3+)-doped or Yb~(3+)-doped single crystale with the structure of perovskite-type or garnet-type

Ce3＋掺杂的单晶体普遍具有高的光输出和快的衰减时间，较为适合于作闪烁晶体，目前是国际上的一个研究热点。Yb3＋掺杂的单晶体由于在中微子探测和超快闪烁探测方面的潜力而在近两三年的时间内开展了闪烁性能的研究，同时该类晶体作为固体激光器中的增益介质也一直得到重视和发展。本文主要研究了Ce：YAIO3，Ce：LoAIO3，Yb：YA03和Yb：Y3A15O12等单晶体的生长、结构和光谱性质等。其主要内容包括如下几个方面：一、Ce：YAlO3（YAP）单晶体。采用温度梯度法生长，晶体开裂，但可以切割得到用于光谱和闪烁性能测试的样品，对开裂的原因进行了分析。在采用温梯法生长Ce：YAP时，得到的晶体为紫色，而用提拉法生长的Ce：YAP晶体却为无色，对温梯法生长的Ce：YAP晶体的色心性质进行了分析，指出其中的色。主要是F＋和O-心，应用这一色心模型成功的解释了分别在氧化和还原气氛中1400℃退火后的晶体颜色，吸收光谱，光输出性能的变化。将Ce：YAP晶体进一步在1680℃氢气退火后，晶体变为黄色，吸收光谱和荧光光谱均发生了较大的变化，初步LaAIO3见吸收对Ce：离子的能级结构和导带的关系，并且运用其较好的解释了Ce：LoAIO3晶片的发光特性。同时指出，由于这种能级结构，Ce：LaAIO3晶体作为闪烁品体的应用前景就不是很乐观了。三、Yb：YAIO3单晶体。采用提拉法生长了Yb掺杂浓度依次为0．5at．％，5at．％，IOat．％，15at．％，20at．％，30at．％的Yb：YAP晶体。观察到了晶胞体积、密度、吸收光谱、荧光光谱和荧光寿命随Yb掺杂浓度的增加而发生变化的一些现象，结合Yb：YAP晶体中的自吸收效应、上转换发光行为和晶格畸变作了相应的解释。对20at．％Yb：YAP晶体的电荷转移发光行为进行了表征。对15at．％Yb：YAP品体和15at％Yb：YAG晶体的光谱参数进行了计算，结果表明15at．％Yb：YAP晶体将有可能在1012nm和1038nln处实现超短脉冲和调谐激光输出。四、对Yb：YAlO3晶体和Yb：Y3A15O12晶体进行了伽马射线辐照处理，并对辐照处理后的晶体在空气中进行了退火处理。根据吸收光谱分析了辐照损伤和恢复机理，首次在这些晶体中观察到了Yb3十和Yb2＋离子之间的转变。五、比较分析了部分掺ce3＋离子晶体和掺Yb3＋离子晶体的能级结构，光谱和性能。从能级结构的角度初步解释了晶体的光谱和性能，同叼还分析了Yb3＋和ce3"共掺可能带来的对晶体闪烁性能和激光性能的影响。Ce3+-doped single crystals are a kind of important scintillators because they have excellent scintillation performance including high light output and fast decay time. The scintillation performance of Yb3+-doped single crystals have been widely studied in recent three years because they are potential candidates applied in neutrino detection and other radiation detections. On the other hand, Yb3+-doped single crystals are also a kind of important laser crystals applied in solid-state laser devices. In this thesis we studied the growth, structure and spectra properties of Ce: YAIO3, Ce: LaA103, Yb: YAIO3 and Yb: Y3AI5O12 single crystals. 1. Ce: YAIO3 single crystal. Ce: YAIO3 was grown by the temperature gradient technique. The cracking phenomenon was analyzed. The as-grown crystal was pink and was turned into colorless after it was annealed at 1400 °C for 20 h in H2 or O2 atmosphere. We proposed a color center model to explain the experiment phenomena including the color changes, the absorption spectra changes and the light yield changes of Ce: YAP crystals before and after annealing. After the Ce: YAP crystal was annealed at 1680 °C in H2 atmosphere, it was turned into yellow and exhibits the characteristic absorption and fluorescence spectra properties of Ce: YAP and Ce: YAG, which indicated that the annealed Ce: YAP crystal contains both YAP phase and YAG phase. Ce: LaA103 single crystal Undoped LaAlCb and Ce-doped LaAlC>3 single crystals were grown by the Czochralski process. According to their absorption spectra, the energy levels structure of Ce3+ in LaA103 single crystal was determined. We also discussed the position of the 5d energy levels of Ce3+ which is relative to the bottom of conduction band of LaAlC>3 host according to their fluorescence spectra. We pointed out that Ce: LaA103 single crystal may not be a good scintillator because its particular energy levels structure. 3. Yb: YAIO3 single crystals Yb: YAP single crystals with different Yb doping concentration (0.5 at.%, 5 at.%, 10 at.%, 15 at.%, 20 at.%, 30 at.%) were grown using the Czochralski method. The density, absorption spectra, and fluorescence spectra of Yb: YAP changed with the increasing of Yb concentration, which was explained through combining with the self-absorption effect, up-conversion phenomena and crystal lattice distortion. The charge transfer luminescence of 20% Yb: YAP was characterized. Through comparing the spectroscopic parameters of 15% Yb: YAP and 15%Yb: YAG, all results indicate that 15 at.% Yb: YAP crystal is a potential candidate used for ultra-short pulses laser and tunable laser when the laser output wavelength is 1012 nm or 1038 nm. 4. Irradiation and annealing on Yb: YAIO3 and Yb: Y3AI5O1? single crystals. Yb: YAIO3 and Yb: Y3AI5O12 single crystals were irradiated by gamma rays and the gamma-irradiated samples were annealed in air at 600 °C. The irradiation damage mechanism and air-annealing mechanism were characterized and discussed through absorption spectra. For the first time, the gamma-irradiation and air-annealing induced valence changes between Yb3+ and Yb2+ ions in Yb: YAP and Yb: YAG single crystals were observed. 5. The energy levels structure, spectra, and performance of some Ce" -doped and Yb -doped crystals were compared and analyzed. According to the energy levels structure of these crystals, their spectra and performance were explained. The effects of co-doping Ce3+ and Yb3+ in a crystal on its scintillation and laser performance were of co-dopi analyzed