Metastable Ni7B3: A New Paramagnetic Boride from Solution Chemistry, Its Crystal Structure and Magnetic Properties
Metastable Ni7B3: A New Paramagnetic Boride from Solution Chemistry, Its Crystal Structure and Magnetic Properties
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DOI：
10.1021/acs.inorgchem.5b01929
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发表时间：
2015-11-16
影响因子：
4.6
通讯作者：
Albert, Barbara
中科院分区：
文献类型：
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作者：
Hofmann, Kathrin;Kalyon, Nalan;Albert, Barbara
我们用低温溶液合成法捕获了一种未知的亚稳硼化物。在氯化镍水溶液中与四氢硼酸钠反应生成无定形的纳米级沉淀物，经热处理后得到单相Ni7B3作为微晶粉末的块体样品。用同步加速器X-射线粉末数据，基于无序Th7Fe3型模型(六方晶系，空间群P6(3)mc，编号186，a=696.836(4)pm，c=439.402(4)pm)计算了其晶体结构。磁性测量揭示了顺磁性，这与量子化学计算是一致的。根据高温X射线衍射和差示扫描量热法，该硼化镍相在300-424℃之间有一个狭窄的稳定窗口。它在350℃左右结晶，然后在375℃以上开始分解形成Ni3B和Ni2B，并在424℃表现出放热效应。
We trapped an unknown metastable boride by applying low-temperature solution synthesis. Single-phase nickel boride, Ni7B3, was obtained as bulk samples of microcrystalline powders when annealing the amorphous, nanoscale precipitate that is formed in aqueous solution of nickel chloride upon reaction with sodium tetrahydridoborate. Its crystal structure was solved based on a disordered Th7Fe3-type model (hexagonal crystal system, space group P6(3)mc, no. 186, a = 696.836(4) pm, c = 439.402(4) pm), using synchrotron X-ray powder data. Magnetic measurements reveal paramagnetism, which is in accordance with quantum chemical calculations. According to high-temperature X-ray diffraction and differential scanning calorimetry this nickel boride phase has a narrow stability window between 300 and 424 degrees C. It crystallizes at ca. 350 degrees C, then starts decomposing to form Ni3B and Ni2B above 375 degrees C, and shows an exothermic effect at 424 degrees C.