材料科学
结构精修
衍射仪
粉末衍射
衍射
碳化钨
X射线
表面粗糙度
粉末衍射仪
结晶学
微观结构
布拉格定律
几何学
光学
复合材料
物理
扫描电子显微镜
化学
数学
作者
W. Pitschke,H. Hermann,N. Mattern
出处
期刊:Powder Diffraction
[Cambridge University Press]
日期:1993-06-01
卷期号:8 (2): 74-83
被引量:60
标识
DOI:10.1017/s0885715600017875
摘要
Measurements of X-ray diffraction patterns of high- T c superconductor and tungsten–carbide powder samples using a Bragg–Brentano diffractometer showed systematic variations of the intensities for different preparation conditions. For specimens with high surface roughness, an angle-dependent decrease of the intensities is observed which is caused by the microabsorption of the X-rays due to the microstructure of the powder sample. In Rietveld analysis, the thermal parameters are strongly influenced by this effect and may tend to negative values. A realistic description of the surface structure of flat powder samples is proposed. Using an analytical approximation for the microabsorption effect and its dependence on the microstructural parameters the Rietveld refinement yields reasonable values for the thermal parameters.
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