Electron Probe Microanalysis of Variable Oxidation State Oxides: Protocol and Pitfalls
Electron Probe Microanalysis of Variable Oxidation State Oxides: Protocol and Pitfalls
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可变氧化态氧化物的电子探针微量分析：协议和陷阱
DOI：
10.1111/ggr.12199
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发表时间：
2018-03-01
影响因子：
3.8
通讯作者：
Xie, Jing
中科院分区：
文献类型：
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作者：
Yang, Shui-Yuan;Zhang, Ruo-Xi;Xie, Jing
地质氧化物材料的电子探针显微分析依赖于化学计量学的考虑来估计待定氧的含量，从而计算ZAF(原子序数、吸收、荧光)基质校正因子，这要求在相应的软件中明确定义阳离子的价态。然而，在存在其他不确定元素或可变价态阳离子的情况下，化学计量比的ZAF校正可能是有问题的。本文分析了几种含这类阳离子的氧化物，即磁铁矿(Fe_3O_4)、赤铁矿(Fe_2O_3)、黑锰矿(Mn3O_4)和铜矿(Cu2O)。我们将不正确的价态重新计算的数据(方法1)与参考值进行比较，发现由于在基质校正中使用了不正确的氧量，结果不正确。在CalcZAF程序中模拟了赤铁矿和磁铁矿的一些固溶体系列，以验证当使用错误的氧气时的相对误差。为了解决这些问题，我们描述了两种准确的方法。方法2使用被分析元素的真实价态。在方法3中，所有的阳离子都以金属的形式进行分析，待测氧的含量由差值确定。由于EPMA软件不允许使用非整数价，因此方法3适用于在不能定义非整数价的情况下具有非整数价或可疑价的阳离子。
Electron probe microanalysis of geological oxide materials relies on stoichiometric considerations to estimate the content of undetermined oxygen and thus calculate ZAF (atomic number, absorption, fluorescence) matrix correction factors, requiring the valences of cations in the corresponding software to be unambiguously defined. However, stoichiometric ZAF corrections may be problematic in the presence of other undetermined elements or variable valence state cations. Herein, we analyse several oxides containing such cations, that is magnetite (Fe3O4), haematite (Fe2O3), hausmannite (Mn3O4) and cuprite (Cu2O). We compare data re‐calculated for incorrect valence states ( Method 1 ) with reference values, revealing incorrect results, due to an incorrect amount of oxygen used in the matrix correction. Some solid‐solution series of haematite and magnetite were also modelled in CalcZAF program to prove the relative errors when the incorrect oxygen is used. To resolve these issues, we describe two accurate methods. Method 2 uses the true valence states of analysed elements. In Method 3, all cations are analysed as metals, with the content of undetermined oxygen determined by difference. As EPMA software does not allow the use of non‐integer valences, Method 3 is applicable to cations with non‐integer or dubious valences in cases where these non‐integer valences cannot be defined.