Crystal chemistry of synthetic hercynite (FeAl2O4) from XRD structural refinements and Mössbauer spectroscopy
Crystal chemistry of synthetic hercynite (FeAl2O4) from XRD structural refinements and Mössbauer spectroscopy
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通过 XRD 结构精修和穆斯堡尔光谱分析合成铁铝尖矿 (FeAl2O4) 的晶体化学
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
H. Annersten
中科院分区：
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作者：
L. Larsson;H. O’Neill;H. Annersten
采用粉末XRD和穆斯堡尔谱研究了水热法和高温烧结法合成的铁铝尖晶石（FeAl 2 O 4）的晶体化学和热行为。在CO2/CO混合气体混合炉中，在控制氧气气氛下，对样品进行不同温度的退火，然后进行淬火。使用XRD粉末图案的Rietveld细化和穆斯堡尔谱两者来确定阳离子分布，其显示随温度无序的规律性增加。反转参数x从500°C下的0.101（5）增加到900°C下的0.187（4），如由XRD测定的。由穆斯堡尔谱得到的数值分别为0.162（8）和0.19（1）。x的增加伴随着氧位置参数u的类似的平滑减小。在900°C以上，晶内无序的淬灭是不可能的。的热行为是异常的，以前调查的简单氧化物尖晶石。这可以解释为铁铝尖晶石的缺陷化学对氧化态变化的极端敏感性，导致在高温下在固溶体中形成三价铁和空位。这种偏离化学计量比的现象可以通过精确的晶格参数测量来定性地跟踪
The crystal chemistry and thermal behaviour of synthetic hercynite (FeAl 2 O 4 ), a normal spinel, produced both hydrothermally and from sintering oxides at high temperatures, were studied by means of powder XRD and Mossbauer spectroscopy. The samples were annealed at different temperatures under controlled oxygen atmosphere in a gas mixture furnace using CO 2 /CO gas mixtures, and subsequently quenched. Both Rietveld refinement of the XRD powder pattern and Mossbauer spectroscopy were used to determine the cation distribution, which shows a regular increase in disorder with temperature. The inversion parameter, x increases from 0.101(5) at 500°C to 0.187(4) at 900°C as determined from XRD. From Mossbauer spectroscopy the figures are 0.162(8) and 0.19(1) respectively. The increase in x is accompanied by a similar smooth decrease of the oxygen positional parameter, u. Quenching of the intracrystalline disorder above 900°C was not possible. The thermal behaviour is anomalous compared to previously investigated simple oxide spinels. This may be explained by the extreme sensitivity of the defect chemistry of hercynite to variations in oxidation state, leading to the formation of ferric iron and vacancies in solid solution at elevated temperatures. This deviation from stoichiometry can be followed qualitatively by accurate lattice parameter measurements