AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_1-x Fe₂O₄和Ni_xMn_1-xFe₂O₄立方相中的Zn²⁺、Ni²⁺、Mn²⁺以及Fe³⁺在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe_0.09³⁺Mn_0.91²⁺)Fe_1.91³⁺Mn_0.09²⁺]O₄,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe_0.11³⁺ Mn_0.89²⁺)Fe_1.89³⁺Mn_0.11²⁺]O₄,均与实验结果符合较好。在锌铁氧体中,室温下Zn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn²⁺和Fe³⁺发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe³⁺在室温下占据在8a亚晶格上,Ni²⁺与剩下另一半的Fe³⁺共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学预测建立了立方相尖晶石结构的Zn_xMn_1-xFe₂O₄、Ni_xMn_1-xFe₂O₄复合体系中阳离子占位行为与热处理温度对占位的影响。

Study of the Site Occupancy Ordering Behaviors of Cations in the AxMn1-xFe2O4 Ferrites (A=Zn, Ni)

Based on the crystal structure of spinel, we applied the thermodynamic ternary sublattices model to investigate the site occupancy ordering behaviors of Zn²⁺, Ni²⁺, Mn²⁺ and Fe³⁺ on the 8a and 16d sublattices in the Zn_xMn_1-xFe₂O₄ and Ni_xMn_1-xFe₂O₄ by combining thermodynamic calculations with first-principles calculations. Our results suggest that in the manganese ferrites, Mn²⁺ occupies the 8a sublattice completely, and Fe³⁺ occupies the 16d sublattice at room temperature, which belongs to a normal spinel. The site configuration is (Fe_0.09³⁺Mn_0.91²⁺) Fe_1.91³⁺Mn_0.09²⁺]O₄. When the ferrite is subjected to the heat treatment of 1 273 K, and when the temperature increases to 1 473 K, the site configuration is (Fe_0.11³⁺Mn_0.89²⁺)Fe_1.89³⁺Mn_0.11²⁺]O₄, which agrees well with the available reliable experimental results. In the zinc ferrites, Zn²⁺ occupies the 8a sublattice completely, and Fe³⁺ completely occupies the 16d sublattice at room temperature. It also belongs to normal spinel, and the cations trend to exchange the site occupancy each other at higher temperature. In the Ni ferrites, Ni²⁺ occupies the 16d sublattice completely, and the Fe³⁺ cations occupy both the 8a and the 16d sublattices, which agrees with the experimental results. It belongs to an inverse spinel. Then, the relationship between the occupancy behaviors and the composition, as well as the heat treatment temperature in the Zn_xMn_1-xFe₂O₄ and Ni_xMn_1-xFe₂O₄ were established based on theoretically predictions.