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首页> 外文期刊>Crystal growth & design >Pseudocubic Crystal Structure and Phase Transition in Doped Ye'elimite
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Pseudocubic Crystal Structure and Phase Transition in Doped Ye'elimite

机译：掺杂Ye'elimite中的伪立方晶体结构和相变

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摘要

Sodalites are tridimensional alumino-silicate materials containing cages where loosely bonded anions are located. Ye'elimite, Ca_4[Al_6O_(12)]SO_4, is outstanding as an aluminate sodalite with a flexible framework accepting several type of dopants with important structural consequences. Moreover, ye'elimite is also important from an applied perspective as it is the most relevant phase in calcium sulfoaluminate cements. The crystal structure of stoichiometric ye'elimite has recently been unraveled, but the structure of dopant-containing ye'elimite, which is present in cements, is not well studied. Here, we report the pseudocubic crystal structure of doped ye'elimite, Ca_(3.8)Na_(0.2)Al_(5.6)-Fe_(0.2)Si_(0.2)O_(12)SO_4, from high-resolution synchrotron powder diffraction data. The powder pattern is indexed with a cubic cell, and a structural model is reported based on the I4-bar3m space group. However, this compound displays diffraction peak narrowing on heating. Furthermore, some high-angle split peaks become a single peak on heating, and a phase transition is measured at 525 ℃. Therefore, it is concluded that the crystal structure at room temperature has a lower symmetry, although it can be described as cubic. The structural study at 800 ℃ suggests a truly cubic structure, and we speculate that this phase transition, on heating, is likely related to the dynamical disordering of the sulfate anions. Finally it is concluded that the high temperature cubic state was not quenchable to ambient, even when the tested chemical substituents are introduced into the structure.
机译：钠方石是三维笼罩的铝硅酸盐材料，在其中放置松散结合的阴离子。 Ye'elimite Ca_4 [Al_6O_（12）] SO_4作为铝酸盐方钠石具有出色的结构，该框架具有灵活的结构，可以接受几种类型的具有重要结构后果的掺杂剂。此外，从应用的角度来看，e石也很重要，因为它是硫铝铝酸钙水泥中最相关的相。最近已经阐明了化学计量的叶limit的晶体结构，但是对存在于水泥中的含掺杂剂的叶e的结构尚未进行充分的研究。在这里，我们从高分辨率同步加速器粉末衍射数据中报告了掺杂石的假立方晶体结构Ca_（3.8）Na_（0.2）Al_（5.6）-Fe_（0.2）Si_（0.2）O_（12）SO_4。用立方单元对粉末图案进行索引，并根据I4-bar3m空间群报告结构模型。但是，该化合物显示出在加热时变窄的衍射峰。此外，一些大角度分裂峰在加热时变成一个峰，并且在525℃下测量到相变。因此，可以得出结论，尽管室温下的晶体结构可以说是立方的，但其对称性较低。在800℃下的结构研究表明是真正的立方结构，我们推测在加热时这种相变可能与硫酸根阴离子的动态无序有关。最后得出结论，即使将测试的化学取代基引入结构中，高温立方状态也无法淬灭至环境温度。

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