Liu Wen-Han

Structure study of Ba2CeCu3O7.4

Abstract Single phase Ba2CeCu3O7.4 was prepared. EXAFS, X-ray diffraction and plasma spectroscopy measurements were performed. A structure model with the cell parameter: a=6.208 A , b=6.232 A and c=8.759 A is proposed based on these experiments. The lack of superconductivity in this system may be caused by the entrance of Ce+4 in Cu-site and the formation of asymmetric [CuO2] plane.

The phase transition in annealed mechanically alloyed Fe - Cu.

Using Mössbauer spectra and x-ray diffraction patterns, annealed mechanically alloyed Fe - Cu has been investigated in this paper. It is found that in [Formula: see text], after it has been milled, fcc-Cu has transformed into bcc-Cu, and some Cu atoms have diffused into the Fe. After the alloy has subsequently been annealed, it is found that bcc-Cu has transformed back into fcc-Cu, while the Cu atoms in the Fe have been separated. In [Formula: see text], after being milled, an fcc-Fe-rich phase has been formed, and after the alloy has subsequently been annealed, this has transformed back to bcc-Fe. The shorter the milling time and the higher the annealing temperature, the faster the transformation. In [Formula: see text], after it has been annealed, the fcc-Fe-rich phase has transformed to bcc-Fe also, and the fcc-Cu-rich phase remains when the annealing temperature increases. All of these results show that the fcc-Fe-rich phase in the milled samples is a metastable phase - it will transform to stable bcc-Fe when it is annealed - while the long-milling-product fcc-Cu-rich phase is a stable phase.

An EXAFS study of SrCaBiCuO superconductor

Abstract We have measured the Cu K edge EXAFS of BiCaSrCuO single crystal superconductor and semiconductor, the nearest coordination around Cu of superconductor phase is agreement with the results obtained from single crystal X-ray diffraction by Sunshine et. al. [1]

Simulation of x-Ray Diffraction of Multilayer Film with Interfacial Roughness

In this paper, the x-ray diffraction profiles of multilayer with uncorrelated rough interfaces are directly simulated using kinematic theory of x-ray diffraction. The result shows that the decrease of the reflective intensity caused by the interfacial roughness is more severe than that caused by random fluctuation of period of the same degree, and the decrease of the reflective intensity of high order Bragg deffraction is more rapid than that of low order ones. So it is very important to reduce the interfacial roughness in the deposition and in the annealing of multilayer films.

Structure model with m35 symmetry and 12 coordinates

Taking into consideration of the main results observed in Al-Mn quasicrystal, we suggest a structure model with m35 symmetry. The grain of quasicrystal can grow up with definite Al and Mn sites and Al:Mn ratio. All atoms in this model have 12 coordinates and all neighboring distances are suitable. Especially, the density deduced from it is in good agreement with experiment.