Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30 alloy
Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30 alloy
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DOI：
10.1154/1.3257906
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发表时间：
2009-12
影响因子：
0.5
通讯作者：
H. Sitepua
中科院分区：
文献类型：
--
作者：
H. Sitepua
优选的方向或纹理是实验粉末图案的共同特征。回顾了两种常用的择优取向模型——March-Dollase 模型和广义球谐模型——的数学原理。这两个模型分别应用于 Rietveld 分析中单轴压制的辉钼矿 (MoO3) 和方解石 (CaCO3) 粉末以及收到的粉末的中子粉末数据。将结构细化结果与单晶结构进行比较。结果表明，使用 March 模型或广义球谐描述都可以获得晶体结构的合理细化。然而，广义球谐描述为辉钼矿和方解石提供了比 March 模型更好的 Rietveld 拟合。因此，建议使用广义球谐描述来校正中子衍射分析中的择优取向，以进行晶体结构细化和相组成分析。随后，广义球谐描述扩展到退火和时效多晶富镍Ni50.7Ti49.30形状记忆合金的晶体结构细化。
Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation—the March-Dollase and the generalized spherical-harmonic models—is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite (MoO3) and calcite (CaCO3) powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni50.7Ti49.30 shape memory alloys.