Radiation-damaged zircon under high pressures
Radiation-damaged zircon under high pressures
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DOI：
10.1007/s00269-018-0978-6
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发表时间：
2018-11-01
影响因子：
1.4
通讯作者：
Mihailova, Boriana
中科院分区：
文献类型：
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作者：
Binvignat, Felipe A. Pina;Malcherek, Thomas;Mihailova, Boriana
利用偏振拉曼光谱和单晶同步辐射X射线衍射技术，对三个具有代表性的锆石样品进行了10 GPa压力下的结构响应分析，这些样品分别表现出可忽略的、中等的和高度的辐射损伤。结果表明，压力不会改变整体的非晶分数，但诱导原子重排在压力类似于2.5和类似于6.5 GPa。第一阈值压力与非晶基体中Si-O键的弱化有关。第二阈值压力标志着共存的非晶和结晶纳米区域的相关响应，即，非晶材料的不可逆致密化的开始和微晶中的辐射诱导应变的不均匀性的减少。后一个过程突然发生在中度变晶锆石（无定形分数类似于54%）的结晶区和更顺利的重变晶锆石（无定形分数类似于84%），由于不同的途径释放的本地应变。详细考虑了动态和静态可压缩性以及各向同性和各向异性Gruneisen参数。辐射损伤使晶体组分的体积压缩系数和晶体声子压缩系数增大，Gruneisen参数减小。
Polarized Raman spectroscopy and single-crystal synchrotron X-ray diffraction were applied to three representative zircon samples exhibiting a negligible, intermediate, and high degree of radiation damage to analyze the pressure-induced structural response up to 10GPa. It is shown that pressure does not change the overall amorphous fraction, but induces atomic rearrangements at pressures of similar to 2.5 and similar to 6.5 GPa. The first threshold pressure is related to weakening of the Si-O bonds in the amorphous matrix. The second threshold pressure marks the correlated response of the coexisting amorphous and crystalline nanoregions, namely, the beginning of irreversible densification of the amorphous material and reduction of inhomogeneity of radiation-induced strain in the crystallites. The latter process occurs abruptly in the crystalline regions of moderately metamict zircon (amorphous fraction similar to 54%) and more smoothly for heavily metamict zircon (amorphous fraction similar to 84%) due to the different pathways of release of the local strains. The dynamic and static compressibilities as well as the isotropic and anisotropic Gruneisen parameters are considered in detail. The radiation damage increases the volume compressibility of the crystalline fraction as well as the crystal phonon compressibilities and decreases the Gruneisen parameters.