Stacking structures in pyrophyllite revealed by high-resolution transmission electron microscopy (HRTEM)
Stacking structures in pyrophyllite revealed by high-resolution transmission electron microscopy (HRTEM)
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DOI：
10.2138/am.2006.1997
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发表时间：
2006-08
影响因子：
3.1
通讯作者：
T. Kogure;M. Jige;J. Kameda;A. Yamagishi;R. Miyawaki;R. Kitagawa
中科院分区：
文献类型：
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作者：
T. Kogure;M. Jige;J. Kameda;A. Yamagishi;R. Miyawaki;R. Kitagawa
摘要利用高分辨率透射电镜（HRTEM）研究了叶蜡石Al2Si4O10(OH)2的层积结构。检查的标本是大板状晶体（俄罗斯乌拉尔的Berosovska）和细板状晶体的大块聚集体（韩国西南部的Nohwa）。两个样品的粉末x射线衍射（XRD）模式与之前报道的2M多型相似。两个样品的共同堆叠顺序并非如先前报道的那样是单斜的，具有两层周期性，而是2:1层的均匀取向和层间位移的两个可选方向几乎完全无序，即两个四面体薄片之间在层间区域的横向位移。层间位移方向与层内位移方向（2:1层内两个四面体薄片之间的横向位移）相差约±2π/3。用该模型模拟的粉末XRD谱图与实验谱图非常接近。板条状Berosovska晶体的延伸与层内位移的方向相对应，如在伊利石- 1m中所见。偶见不同走向的2:1层，层间位移与层内位移几乎平行，为层间断层。这种紊乱在巨大的Nohwa标本中比在Berosovska标本中更频繁地发生。在Nohwa试样中发现了2M层序的亚微米域，层间位移的两个方向有规律地交替。
Abstract Stacking structures in pyrophyllite, Al2Si4O10(OH)2, were investigated mainly by using high-resolution transmission electron microscopy (HRTEM). The specimens examined were large lath-shaped crystals (Berosovska, Urals, Russia) and massive aggregates of fine platy crystals (Nohwa, southwest Korea). Both specimens showed powder X-ray diffraction (XRD) patterns similar to those reported previously as the 2M polytype. The common stacking sequence in the two specimens is not monoclinic with two-layer periodicity as previously reported, but a uniform orientation of the 2:1 layers and near complete disorder of two alternative directions of interlayer displacement, i.e., lateral displacement between the two tetrahedral sheets across an interlayer region. The directions of interlayer displacement are about ± 2π/3 from that of the intralayer shift (lateral displacement between the two tetrahedral sheets within a 2:1 layer). Simulation of powder XRD patterns by this stacking model closely approximates the experimental pattern. Elongation of the lath-shaped Berosovska crystals corresponds to the direction of the intralayer shift, as seen in illite-1M. 2:1 layers with different orientations, and interlayer displacement almost parallel to the intralayer shift, were occasionally observed as stacking faults. Such disorder occurs more frequently in the massive Nohwa specimen than in the Berosovska specimen. Sub-micrometer domains of the 2M stacking sequence with regular alternation of the two directions of interlayer displacement were found in the Nohwa specimen.