Sr：BaF2中的F型色心的电子结构及转型及理研究

本文运用嵌入原子簇的电荷自治离散变分方法（ＤＶＭ－Ｘα方法）分别对Ｓｒ：ＢａＦ２晶体中Ｆ,Ｆ＾＋和ＦＡ「Ｓｔ＾２＋」心的能级结构进行了计算,得到了Ｆ,Ｆ＾＋和ＦＡ「Ｓｉ＾２＋」心的光学吸收跃迁模式,其跃迁能量分别是１．９１ｅＶ,１．８９ｅＶ,２．１３ｅＶ。我们认为,经电子辐照后的Ｓｒ：ＢａＦ２晶体,在光吸收实验中测到的６４０ｎｍ（１．９４ｅＶ）,８４０ｎｍ（２．１５ｅＶ）两个峰分别是由于电子辐照过     

Sr∶BaF2中的F型色心的电子结构及转型机理研究

本文运用嵌入原子簇的电荷自洽离散变分方法(DVM-Xα方法)分别对Sr∶BaF2晶体中F,F+和FA[Sr2+]心的能级结构进行了计算,得到了F,F+和FA[Sr2+]心的光学吸收跃迁模式,其跃迁能量分别是1.91eV,1.89eV,2.13eV.我们认为,经电子辐照后的Sr∶BaF2晶体,在光吸收实验中测到的640nm(1.94eV),840nm(2.15eV)两个峰分别是由于电子辐照过程中形成的F和FA[Sr2+]心的吸收峰,在光诱导下并存在着F→FA[Sr2+]心的可逆转换过程.本文的计算结果合理地解释了实验所观测到的现象.     

温度梯度法生长Er:BaY2F8晶体开裂现象的研究

对温度梯度法生长Er:BaY2F8晶体的开裂现象进行了研究,从理论上讨论了温场分布、生长速率、热应力和稀土离子掺杂对晶体开裂的影响,并通过实验分析了垂直于解理面方向上膨胀系数的变化对晶体开裂造成的影响.研究结果表明:晶体生长时径向温度梯度越小越好,生长晶体的最佳工艺参数为直径为10 mm,最佳轴向温度梯度为6 ℃/mm,最佳生长速率为0.2～0.3 mm/h.通过缓慢降温,可以成功避免晶体的开裂.     

退火和电子辐照复合处理对ZnGeP2单晶性能的改进研究

采用退火和电子辐照相结合的复合工艺方法,对ZnGeP2晶体进行生长后处理.采用傅里叶红外光谱仪(FTIR)和高阻仪(HRM)等,对经不同次序的复合工艺处理前后样品的红外透过率和电阻率进行了测试.结果表明,采用先退火后电子辐照的复合处理工艺,样品的红外透过率能得到明显的提高.     

Nd:NaY(WO4)2激光晶体光谱性能研究

Nd:NaY(WO4)2 是一种性能优良的激光晶体.本文采用提拉法生长了Nd:NaY(WO4)2晶体,测试了该晶体的吸收光谱和光荧光光谱.结果表明,该晶体在804nm、752nm、586nm附近有较强、较宽的吸收峰,适合于LD泵浦.从光荧光光谱得到发射波长分别为1064nm和1350nm,并计算了晶体的吸收截面和发射截面.     

The Influence of High Temperature Predeformation on Ductility of LiF and BaF2 Single Crystals

The effect of high temperature predeformation on deformation characteristics of ductile LiF and brittle BaF₂ crystals was investigated. The same predeformation, as has been shown previously, leads to the increasing of the limited plastic deformation of MgO crystals by one order of magnitude. It was found that in both investigated crystals, as in the case of MgO crystals, at the test temperature T₂ ≅ 0.1 T_m limited plastic deformation before fracture obviously increases if the specimen was prestrained up to ε_p ≦ 1% at T₁ = 0.5 T_m. This increase is as higher as the plasticity of crystal is lower. In BaF₂ crystals it reaches a factor of 20 and more. The effect is connected with the creation of mobile dislocations during the high temperature predeformation and dislocaton sources for subsequent deformation at lower temperatures and with the homogeneity of the process of plastic deformation. These conditions prevent the appearance of dangerous places in which the fracture can begin.     

Electron Spin Resonance In CuCrS2 and CuCrSe2 Single Crystals

Abstract

Single crystal ESR spectra of CuCrS₂ and CuCrSe₂ have been measured at both X- and Q-band frequencies. Anisotropic signals from the localised Cr³⁺ d-electrons give zero-field splitting parameters of 0.29cm^?1 and 0.31cm^?1 for the sulphide and selenide respectively, suggesting a possible orbital interaction between the Cr and Cu ions. The dependence of the ESR parameters on temperature shows the effect of magnetic ordering.     

电子束蒸发制备PbI2膜及其光学性能研究

采用电子束蒸发法制备PbI2膜,研究不同工艺参数对制备样品光学性质的影响.结果表明,制备样品属于六方相多晶结构,随衬底温度的升高,样品中的I元素含量降低并趋于理想化学配比.随着衬底温度的升高,PbI2膜的光谱透过性能逐渐改善,吸收边沿低能一侧的拖尾逐步消除,源自样品结晶质量的提高.根据紫外-可见透过谱,计算了不同条件下制备样品的厚度、折射率、吸收系数和光学带隙.结果发现,随衬底温度的升高,制备样品的折射率和光学带隙出现波动变化,但吸收系数单调增大.在相同的衬底温度下,35 cm的源-衬间距下制备的样品具有最大的光吸收系数,归因于该系列样品较高的致密度.     

Density,Colourability and Conductivity of Sr2+ Doped KCl Crystals

The measurements of colourability and density changes in KCl crystals with different Sr²⁺ contents point to the presence of two separate doping ranges in which different mechanisms of Sr²⁺ incorporation are active. Below 350 ppm Sr/KCl substitutional incorporation and above 350 ppm Sr/KCl precipitation of a second phase predominates. The latter process is accompanied by the formation of larger vacancy clusters. Ionic conductivity measurements imply that in the range between 80 and 350 ppm the aggregation of Sr²⁺ [+] dipols takes place.     

电子束蒸发制备ZnO:Al透明导电膜及其性能研究

在本实验中我们利用电子束蒸发方法在玻璃衬底上制备了ZnO:A l透明导电膜,并对所得样品在400℃下进行了退火处理。利用扫描电子显微镜观察了样品的表面形貌,利用分光光度计分析了样品的光学性质,结果表明所得样品在可见光范围具有较好的透光性。利用四探针对其进行了电学性质的测量,表明衬底温度为200℃时制备的样品电阻率可达6×10-3Ω.cm。     

Investigation of the Polytypism in Layered CdInGaS4 Crystals by Electron Diffraction Methods

Crystallography Reports - The polytypism in layered CdInGaS4 crystals grown by chemical transport reaction has been investigated by previously developed methods of oblique-texture electron...     

Electron Microscopy and X-ray Study of the Growth of FeCr2S4 Spinel Single Crystals by Chemical Vapour Transport

The growth features of FeCr₂S₄ spinel single crystals prepared by chemical vapour transport were studied by means of scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy, electron diffraction and X-ray analysis. Our results indicate that the epitaxial growth of the new phases FeCr₇S₁₂ and FeCr₈S₁₂, both based on the NiAs structure, can essentially inhibit the growth of large FeCr₂S₄ spinel single crystals in the octahedral habit. The new phases are fully characterised and the effects of defect ordering in these new phases are also reported.