用西门子 D-500型衍射仪,CuK_α辐射测量了一组不同掺镁浓度 LiNbO_3的 X 射线粉末衍射谱。样品的掺镁浓度分别为0、1.0、2.7、5.0、6.0、9.0(mol%,x=0.945)。X 射线衍射结果表明各样品均未发生相变或相分离。用最小二乘法(2θ=90°...用西门子 D-500型衍射仪,CuK_α辐射测量了一组不同掺镁浓度 LiNbO_3的 X 射线粉末衍射谱。样品的掺镁浓度分别为0、1.0、2.7、5.0、6.0、9.0(mol%,x=0.945)。X 射线衍射结果表明各样品均未发生相变或相分离。用最小二乘法(2θ=90°～150°)得到了各组分的精密点阵常数 a、c。结果表明掺镁浓度低于阈值样品的点阵常数无明显变化,而高于阈值样品的点阵常数则有明显增大。用阿基米德法测量了上述样品的密度,按我们提出的缺陷结构模型计算所得的 X 射线密度与实测密度比较,发现两者变化趋势和绝对值都较吻合。上述实验结果证明:在掺镁浓度低于阈值时,Mg^(2+)进入 Li 位;而当掺镁浓度超过阈值时,Mg^(2+)则进入 Nb 位。这与我们早先二篇文章的结果是一致的。展开更多
XPS(X 光电子能谱)测量结果表明:YBaCuO 陶瓷的 Ba 3d 谱线由两种不同结合能的 Ba 3d 谱线组成,它们的相对强度随烧结温度不同而有明显差异,其临界温度 T_c 也不同。它们可能对应于不同相的 YBaCuO化合物,其相对含量因烧结条件而异。本...XPS(X 光电子能谱)测量结果表明:YBaCuO 陶瓷的 Ba 3d 谱线由两种不同结合能的 Ba 3d 谱线组成,它们的相对强度随烧结温度不同而有明显差异,其临界温度 T_c 也不同。它们可能对应于不同相的 YBaCuO化合物,其相对含量因烧结条件而异。本文还研究了 Ar^+离子轰击对 YBa_2Cu_3O_(7-x)超导陶瓷的影响,离子轰击后,呈单一的 Ba 3d 谱线,Cu 2p 谱线则还原为较低的价态,其效果与真空退火处理十分相似。展开更多
LiNbO<sub>3</sub> crystal and waveguide have been widely used as electro-optical,acousto-optical and nonlinear-optical materials. But photorefractive effects often seriously impede the application of the c...LiNbO<sub>3</sub> crystal and waveguide have been widely used as electro-optical,acousto-optical and nonlinear-optical materials. But photorefractive effects often seriously impede the application of the crystal as photoelectronic device. It has been reported that the resistance to the optical-damage of congruent LiNbO<sub>3</sub> with added 4.6% MgO can be about展开更多
This paper presents measurements of OH- absorption bands, fundamental optical absorption edge, lattice parameters, density, color center absorption spectra and Fe3+ ESR spectra at room temperature for a series of magn...This paper presents measurements of OH- absorption bands, fundamental optical absorption edge, lattice parameters, density, color center absorption spectra and Fe3+ ESR spectra at room temperature for a series of magnesium-doped and iron-doped lithium nio-bate crystals, and their dependence on magnesium concentration. It is observed that there exists the threshold effect of the magnesium dopant concentration in the measurements. The influence of the magnesium ion on the defect structure of magnesium-doped LiNbO3 crystal is studied by use of the defect chemistry. The formation of various defect lattices in the crystal at different magnesium dopant concentrations, their growth and decay rules are proposed. Calculations indicate that the defect lattice with Nb-site Mg2+ will be formed in a congruent LiNbO3 crystal when the MgO-doping level reaches 5.3%, which is taken as the main mark of the 'threshold'. The change caused by the 'threshold' in the ionic environment of the LiNbO3 crystal will serve to demonstrate the experimental results. And the calculation of the threshold concentration coincides with experiments. The conclusion in this paper can explain the reason for the drastic increase of anti-optical-damage capability in highly magnesium-doped LiNbO3. This is significant for the research on the modification of other ABO,-type electro-optic crystals.展开更多
文摘用西门子 D-500型衍射仪,CuK_α辐射测量了一组不同掺镁浓度 LiNbO_3的 X 射线粉末衍射谱。样品的掺镁浓度分别为0、1.0、2.7、5.0、6.0、9.0(mol%,x=0.945)。X 射线衍射结果表明各样品均未发生相变或相分离。用最小二乘法(2θ=90°～150°)得到了各组分的精密点阵常数 a、c。结果表明掺镁浓度低于阈值样品的点阵常数无明显变化,而高于阈值样品的点阵常数则有明显增大。用阿基米德法测量了上述样品的密度,按我们提出的缺陷结构模型计算所得的 X 射线密度与实测密度比较,发现两者变化趋势和绝对值都较吻合。上述实验结果证明:在掺镁浓度低于阈值时,Mg^(2+)进入 Li 位;而当掺镁浓度超过阈值时,Mg^(2+)则进入 Nb 位。这与我们早先二篇文章的结果是一致的。
文摘XPS(X 光电子能谱)测量结果表明:YBaCuO 陶瓷的 Ba 3d 谱线由两种不同结合能的 Ba 3d 谱线组成,它们的相对强度随烧结温度不同而有明显差异,其临界温度 T_c 也不同。它们可能对应于不同相的 YBaCuO化合物,其相对含量因烧结条件而异。本文还研究了 Ar^+离子轰击对 YBa_2Cu_3O_(7-x)超导陶瓷的影响,离子轰击后,呈单一的 Ba 3d 谱线,Cu 2p 谱线则还原为较低的价态,其效果与真空退火处理十分相似。
基金Project supported by the National Natural Science Foundation of China,the Chinese manuscript of this note was published in Kexue Tongbao(Chinese Edition)in July 1988.
文摘LiNbO<sub>3</sub> crystal and waveguide have been widely used as electro-optical,acousto-optical and nonlinear-optical materials. But photorefractive effects often seriously impede the application of the crystal as photoelectronic device. It has been reported that the resistance to the optical-damage of congruent LiNbO<sub>3</sub> with added 4.6% MgO can be about
基金Project supported by the National Natural Science Foundation of China
文摘This paper presents measurements of OH- absorption bands, fundamental optical absorption edge, lattice parameters, density, color center absorption spectra and Fe3+ ESR spectra at room temperature for a series of magnesium-doped and iron-doped lithium nio-bate crystals, and their dependence on magnesium concentration. It is observed that there exists the threshold effect of the magnesium dopant concentration in the measurements. The influence of the magnesium ion on the defect structure of magnesium-doped LiNbO3 crystal is studied by use of the defect chemistry. The formation of various defect lattices in the crystal at different magnesium dopant concentrations, their growth and decay rules are proposed. Calculations indicate that the defect lattice with Nb-site Mg2+ will be formed in a congruent LiNbO3 crystal when the MgO-doping level reaches 5.3%, which is taken as the main mark of the 'threshold'. The change caused by the 'threshold' in the ionic environment of the LiNbO3 crystal will serve to demonstrate the experimental results. And the calculation of the threshold concentration coincides with experiments. The conclusion in this paper can explain the reason for the drastic increase of anti-optical-damage capability in highly magnesium-doped LiNbO3. This is significant for the research on the modification of other ABO,-type electro-optic crystals.
