The anomaly of LiNbO3 in the vicinity of 75℃ has been studied by various X-ray diffraction methods.An abrupt change of axial ratio(c/a)was measured,which may be ascribed to alternate rotation of NbO6 octahedron about...The anomaly of LiNbO3 in the vicinity of 75℃ has been studied by various X-ray diffraction methods.An abrupt change of axial ratio(c/a)was measured,which may be ascribed to alternate rotation of NbO6 octahedron about c axis.No change of structure symmetry was observed.展开更多
K_(o)-image of the Brazil twin boundary in quartz crystal by X-ray section topography and the same contrasts of the first fringes for entrance and exit surface are shown in this paper.
用 X 射线衍射法仔细观察了高 T_c 超导材料 YB_2Cu_3O_(7-x)中四方与正交相的结构转变过程,认为此类结构转变属二级或近似二级相变。它与样品经不同温度退火后的氧含量密切有关,表现在其 X 射线衍射轮廓上的某些细微变化可用来判别其...用 X 射线衍射法仔细观察了高 T_c 超导材料 YB_2Cu_3O_(7-x)中四方与正交相的结构转变过程,认为此类结构转变属二级或近似二级相变。它与样品经不同温度退火后的氧含量密切有关,表现在其 X 射线衍射轮廓上的某些细微变化可用来判别其氧含量的范围,以及其吸,放氧过程;如将氧的有序化或作为一种序参量来讨论该材料的超导电性能将是非常有用的。展开更多
用 X 射线旋进照相、电子衍射和 TEM 方法观察到 Bi 系超导材料中某些类多型结构特征,显示了一维无序结构及衍射的弧化效应、带状结构均与它存在交生现象有关;用类多型结构特征阐明 BiO 层结构中 Bi^(+++)的位移将导致 BiO 层中多余的...用 X 射线旋进照相、电子衍射和 TEM 方法观察到 Bi 系超导材料中某些类多型结构特征,显示了一维无序结构及衍射的弧化效应、带状结构均与它存在交生现象有关;用类多型结构特征阐明 BiO 层结构中 Bi^(+++)的位移将导致 BiO 层中多余的氧正是其超导电性改变的一种标志。展开更多
Ⅰ. INTRODUCTIONAfter H. Maeda et al. discovered a high T_c superconductor in the Bi-Sr-Ca-Cu-O system, which does not contain any notable rare-earth element, Z. Z. Sheng et al. discovered subsequently another high T_...Ⅰ. INTRODUCTIONAfter H. Maeda et al. discovered a high T_c superconductor in the Bi-Sr-Ca-Cu-O system, which does not contain any notable rare-earth element, Z. Z. Sheng et al. discovered subsequently another high T_c superconductor in T1-Ba-Ca-Cu-O system. Its T_c seems higher than Bi-system. The crystal structure and superconductivity of both oxides were stated to be either identical or isomorphous. There are two or three superconductive phases with T_c～85 K and ～105 K or even higher. These phases are of 2212 and 2223, or even of more different in chemical composition, usually called as the lower and the higher superconductive phases. A number of studies were carried out to explore a pure single superconductive phase with different treatments and to find out their structure relation for these phases.展开更多
文摘The anomaly of LiNbO3 in the vicinity of 75℃ has been studied by various X-ray diffraction methods.An abrupt change of axial ratio(c/a)was measured,which may be ascribed to alternate rotation of NbO6 octahedron about c axis.No change of structure symmetry was observed.
文摘K_(o)-image of the Brazil twin boundary in quartz crystal by X-ray section topography and the same contrasts of the first fringes for entrance and exit surface are shown in this paper.
文摘用 X 射线衍射法仔细观察了高 T_c 超导材料 YB_2Cu_3O_(7-x)中四方与正交相的结构转变过程,认为此类结构转变属二级或近似二级相变。它与样品经不同温度退火后的氧含量密切有关,表现在其 X 射线衍射轮廓上的某些细微变化可用来判别其氧含量的范围,以及其吸,放氧过程;如将氧的有序化或作为一种序参量来讨论该材料的超导电性能将是非常有用的。
文摘Ⅰ. INTRODUCTIONAfter H. Maeda et al. discovered a high T_c superconductor in the Bi-Sr-Ca-Cu-O system, which does not contain any notable rare-earth element, Z. Z. Sheng et al. discovered subsequently another high T_c superconductor in T1-Ba-Ca-Cu-O system. Its T_c seems higher than Bi-system. The crystal structure and superconductivity of both oxides were stated to be either identical or isomorphous. There are two or three superconductive phases with T_c～85 K and ～105 K or even higher. These phases are of 2212 and 2223, or even of more different in chemical composition, usually called as the lower and the higher superconductive phases. A number of studies were carried out to explore a pure single superconductive phase with different treatments and to find out their structure relation for these phases.
