Anelastic behaviour of leucite KAlSi2O6
Anelastic behaviour of leucite KAlSi2O6
复制标题
白榴石 KAlSi2O6 的滞弹性行为
DOI：
10.1016/j.msea.2006.02.233
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发表时间：
2006
期刊：
影响因子：
6.4
通讯作者：
S. Redfern
中科院分区：
文献类型：
--
作者：
J. Walsh;R. Harrison;S. Redfern
本文研究了白榴石KAlSi_2O_6对调频应力的滞弹性响应。白榴石是一种天然存在的开放框架铝硅酸盐，与方沸石（沸石化合物）密切相关，存在于地壳中。它显示了在[公式：见正文] 665°C和[公式：见正文] 645°C下的两个相变，从立方Ia 3d通过I41/acd到I41/a。因此，低温I41/a相包含片晶和半面体孪晶;中间I41/acd相仅包含片晶孪晶。白亮晶通常显示高密度的双壁。最近的研究表明，层状微观结构可以通过双壁运动引起滞弹性软化[R. J. Harrison，S.A.T. Redfern，J.Appl.Phys.95（2004）1706-1717; R.J. Harrison，S.A.T. Redfern，E.K.H. Salje，Phys. Rev. B 69（2004）144101-1-144101-10; R.J. Harrison，S.A.T. Redfern，J. Street，Am. 88（2003）574-582]。这可能是地壳和地幔岩石中地震衰减的一种机制。我们建议，这一过程也发生在白榴石的动力学力学分析的结果的基础上。在含孪晶白榴石单晶体上以三点弯曲方式施加调频应力（0.4- 16 Hz）。动态模量和tanδ函数已被测量，虽然这些是部分模糊的存在下的高温相变。双壁运动的表观活化能（600 kJmol − 1或更高）异常高，表明可能依赖于硅在铝硅酸盐框架内的扩散。软化的模量在高温立方相，对Ia 3d到I41/acd过渡冷却，是一致的耦合到光学模式，显示出强色散与三个声子分支软化相等在所有方向。
An examination of the anelastic response of leucite, KAlSi2O6, to frequency modulated stress is presented. Leucite is a naturally occurring open framework aluminosilicate closely related to analcime (a zeolite compound) and is found in the earth's crust. It shows two phase transitions at [Formula: see text] 665°C and [Formula: see text] 645°C, from cubic Ia3d through I41/acd to I41/a. Consequently the low temperature I41/a phase contains both lamellar and merohedral twins; the intermediate I41/acd phase contains lamellar twins only. Leucites typically show a high density of twin walls. Recent studies have shown that lamellar microstructures can give rise to anelastic softening via twin wall motion [R.J. Harrison, S.A.T. Redfern, J. Appl. Phys. 95 (2004) 1706–1717; R.J. Harrison, S.A.T. Redfern, E.K.H. Salje, Phys. Rev. B 69 (2004) 144101-1–144101-10; R.J. Harrison, S.A.T. Redfern, J. Street, Am. Mineral. 88 (2003) 574–582]. This could be a mechanism for seismic attenuation in crustal and mantle rocks. We propose that this process also occurs in leucite on the basis of results of dynamical mechanical analysis. A frequency modulated stress (0.4–16Hz) was applied in three point bend geometry to single crystals of leucite containing twins. The dynamic modulus and tanδ functions have been measured, though these are partially obscured by the presence of the higher temperature phase transition. The apparent activation energies for twin wall motion (600kJmol−1or more) are unusually high, suggesting possible dependence on silicon diffusion within the aluminosilicate framework. Softening of the modulus in the high-temperature cubic phase, on cooling towards the Ia3d to I41/acd transition, is consistent with coupling to optic modes which show strong dispersion with three phonon branches softening equally in all directions.