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首页> 外文期刊>Contributions to Mineralogy and Petrology >A thermodynamic model of Fe–Cr spinels
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A thermodynamic model of Fe–Cr spinels

机译：Fe-Cr尖晶石的热力学模型

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A new thermodynamic model for multi-component spinel solid solutions has been developed which takes into account thermodynamic consequences of cation mixing in spinel sublattices. It has been applied to the evaluation of thermodynamic functions of cation mixing and thermodynamic properties of Fe3O4–FeCr2O4 spinels using intracrystalline cation distribution in magnetite, lattice parameters and activity-composition relations of magnetite–chromite solid solutions. According to the model, cation distribution in binary spinels, (Fe 1-x 2+ Fe x 3+ )[Fe x 2+ Fe 2-2y-x 3+ Cr2y ]O4, and their thermodynamic properties depend strongly on Fe2+–Cr3+ cation mixing. Mixing of Fe2+–Fe3+ and Fe3+–Cr3+ can be accepted as ideal. If Fe2+, Fe3+ and Cr are denoted as 1, 3 and 4 respectively, the equation of cation distribution is −RT ln(x 2/((1−x)(2−2y−x)))= ΔG 13 * + (1−2x)W 13+y(W 14−W 13−W34) where ΔG 13 * is the difference between the Gibbs energy of inverse and normal magnetite, W ij is a Margules parameter of cation mixing and ΔG 13 * , J/mol =−23,000+13.4 T, W 14=36 kJ/mol, W 13=W 34=0. The positive nonconfigurational Gibbs energy of mixing is the main reason for changing activity–composition relations with temperature. According to the model, the solvus in Fe3O4–FeCr2O4 spinel has a critical temperature close to 500°C, which is consistent with mineralogical data.
机译：已开发出一种新的多组分尖晶石固溶体热力学模型，该模型考虑了尖晶石亚晶格中阳离子混合的热力学后果。利用磁铁矿中晶内阳离子分布，晶格参数和活性，将其用于阳离子混合的热力学函数和Fe3 O4 –FeCr2 O4 尖晶石的热力学性质的评价-铬铁矿固溶体的组成关系。根据该模型，阳离子在二元尖晶石中的分布为（Fe 1-x 2 + Fe x 3 + ）[Fe x 2 + Fe 2-2y-x 3 + Cr2y ] O4 ，其热力学性质强烈依赖于Fe2 + -Cr3 + 阳离子的混合。 Fe2 + –Fe3 + 和Fe3 + –Cr3 + 的混合是理想的。如果Fe2 + ，Fe3 + 和Cr分别表示为1、3和4，则阳离子分布方程为-RT ln（x 2 /（（1-x）（2- 2y−x））））=ΔG13 * +（1−2x）W 13 + y（W 14 -W 13 -W34 ），其中ΔG13 * 是反磁和正常磁铁矿的吉布斯能量之差，W ij 是阳离子混合的Margules参数，ΔG13 * < / sup>，J / mol = -23,000 + 13.4 T，W 14 = 36 kJ / mol，W 13 = W 34 = 0。正非构型吉布斯混合能是随温度变化的活动-成分关系的主要原因。根据该模型，Fe3 O4 –FeCr2 O4 尖晶石中的固溶体的临界温度接近500°C，这与矿物学数据一致。

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