Floating Zone Growth of Large and Defect-free Ca12Al14O33 Single Crystals
Floating Zone Growth of Large and Defect-free Ca12Al14O33 Single Crystals
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DOI：
10.1021/cg400406t
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发表时间：
2013-07-01
影响因子：
3.8
通讯作者：
Syrowatka, Frank
中科院分区：
文献类型：
--
作者：
Ebbinghaus, Stefan G.;Krause, Holger;Syrowatka, Frank
本文叙述了用浮区法生长Ca_（12）Al_（14）O_（33）（C_（12）A_7，钙铝石）长数厘米、直径达1.5厘米的高质量单晶。与先前的报道相反，使用了氧含量降低的气氛（2%O-2/98%N-2）。熔融区大气泡的形成以及I晶体中微小气体包裹体的存在是浮区生长的主要障碍。为了避免这两个问题，应用了两步结晶。在第一步骤中，多晶进料棒以5 min/h的相对高的速度结晶，而在第二熔化步骤中，应用0.2mm/h的低生长速度。硅或锆的污染被确定为另一个严重问题。这种污染可以通过使用由聚酰胺制成的研磨装置来避免。所获得的晶体优选< 211 >在棒3d上平行于立方空间群I（4）的方向生长。它们是完全透明的，适用于光学研究和单晶中子衍射。
The growth of high-quality single,crystals of Ca12Al14O33 (C12A7, mayenite) with lengths of several centimeters and diameters of up to 1.5 cm by the floating zone technique is described. In contrast to earlier reports, an atmosphere with reduced oxygen content (2% O-2/98% N-2) was used. The formation of large gas bubbles in the molten zone as well as the presence of tiny gas inclusions in the I crystals are the main obstacles of the floating zone growth. In order to avoid both problems, a two-step crystallization was applied. In the first step, the polycrystalline feed rod was crystallized with a comparatively high speed of 5 min/h, while in the second melting step a low growth speed of 0.2 mm/h was applied. Contaminations by silicon or zirconium were identified as an additional severe problem. Such contaminations can be avoided using grinding devices made of polyarnide. The crystals obtained grow preferably parallel to the < 211 >-direction of the cubic space group I (4) over bar 3d. They are completely transparent and suited for optical investigations and single-crystal neutron diffraction.