Reversible Triclinic-Rhombohedral Phase Transition in LiHf2(PO4)3: Crystal Structures from Neutron Powder Diffraction
Reversible Triclinic-Rhombohedral Phase Transition in LiHf2(PO4)3: Crystal Structures from Neutron Powder Diffraction
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LiHf2(PO4)3 中的可逆三斜-菱面体相变：中子粉末衍射的晶体结构
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
S. Bruque
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作者：
E. R. Losilla;M. Aranda;M. Martínez;S. Bruque
合成了单相LiHf2（PO4）3晶体。它显示了在235 K的相变，其特征在于通过DSC，低温X射线衍射，和离子电导率测量。在175和320 K下用中子粉末衍射确定了这两个相的晶体结构。室温相为菱方体R3c，Z = 6，a = 8.8306（1）A和c = 22.0270（5）A，结构经Rietveld方法修正为Rwp = 6.29%，RF = 4.68%。该框架类似于NASICON材料所显示的，Li阳离子从M1位置无序排列，靠近M1−M2瓶颈位置。晶体学精炼的组成是Li0.87Hf2.032（PO4）3，与化学分析一致。低温相为三斜晶系C1，Z = 4，a = 15.2680（4）A，B = 8.6946（3），c = 9.0722（2）A，α = 89.323（2）°，β = 123.740（2）°，γ = 90.666（2）°，结构精修为Rwp = 4.61%，RF = 2.25%。这是一个常见的可逆订单。
Crystalline single-phase LiHf2(PO4)3 has been synthesized. It shows a phase transition at 235 K that has been characterized through DSC, low-temperature X-ray diffractometry, and ionic conductivity measurements. The crystal structures of the two phases have been established by neutron powder diffraction at 175 and 320 K. The room-temperature phase is rhombohedral R3c, Z = 6, a = 8.8306(1) A and c = 22.0270(5) A and the structure has been refined by the Rietveld method to Rwp = 6.29% and RF = 4.68%. The framework is similar to that shown by NASICON materials with the Li cations disordered out of the M1 position and close to the M1−M2 bottleneck site. The crystallographically refined composition was Li0.87Hf2.032(PO4)3 in agreement with the chemical analysis. The low-temperature phase is triclinic C1, Z = 4, a = 15.2680(4) A, b = 8.6946(3), c = 9.0722(2) A, α = 89.323(2)°, β = 123.740(2)°, and γ = 90.666(2)°, and the structure has been refined to Rwp = 4.61% and RF = 2.25%. This is a common reversible ord...