Spinodal Decomposition in the Mg-Al-Fe-O System
Spinodal Decomposition in the Mg-Al-Fe-O System
复制标题
Mg-Al-Fe-O 系中的旋节线分解
DOI：
10.1021/acs.inorgchem.2c02843
复制
发表时间：
2022
影响因子：
4.6
通讯作者：
T. Fujii
中科院分区：
文献类型：
--
作者：
Y. Kusano;T. Furuta;R. Maki;T. Ogawa;T. Fujii
在1573 K下，在空气中使用常规固态反应，随后在冰水中淬火，制备具有Mg/Al/Fe = 0.5：1.0：1.5的标称组成比的过饱和尖晶石固溶体。基于Rietveld精修和热重分析，确定所得到的尖晶石结构化合物（尖晶石）的式为（Mg 0.50AlFe 0.262 + Fe 1.243+）0.97 O 4，表明具有混合价态的Fe的阳离子缺乏的尖晶石结构。发现该尖晶石在855 K以下发生失稳分解，生成γ-Fe 2 O3和改性贫铁尖晶石结构化合物。的旋节温度估计使用的边带出现在X射线衍射图案除了磁化强度值的温度依赖性。这种亚稳分解伴随着Fe 2+到Fe 3+的氧化，并产生了独特的网格状微结构（网格宽度约为25 nm），沿着增强了材料的饱和磁化强度。在空气中以1573 K加热后在炉中冷却至室温的样品具有宽度约为0.1 μm的片层结构，并且包括在其表面上具有γ-Fe 2 O3和贫Fe尖晶石化合物的混合物的颗粒。随后在空气中将该相同材料加热至1373 K，在颗粒中形成ε-Fe 2 O3。ε-Fe 2 O3与改性尖晶石结构化合物的晶体学关系为a ε// [112 <$]s，Bε// [1 <$10]s，c ε// [111]s（ε和s分别表示ε-Fe 2 O3和尖晶石）。
A supersaturated spinel solid solution having a nominal compositional ratio of Mg/Al/Fe = 0.5:1.0:1.5 was prepared using a conventional solid-state reaction at 1573 K in air followed by quenching in ice water. The formula of the resulting spinel structure compound (the spinel) was determined to be (Mg0.50AlFe0.262+Fe1.243+)0.97O4based on a Rietveld refinement and thermogravimetry, indicating a cation-deficient spinel structure having mixed valences of Fe. This spinel was found to decompose to γ-Fe2O3and a modified, Fe-poor spinel structure compound via a spinodal decomposition below 855 K. The spinodal temperature was estimated using the sidebands appearing in X-ray diffraction patterns in addition to the temperature dependence of magnetization values. This spinodal decomposition was accompanied by the oxidation of Fe2+to Fe3+and produced a unique grid-like microstructure (with a grid width of approximately 25 nm) along with enhancement of the saturated magnetization of the material. A sample cooled to room temperature in a furnace after heating at 1573 K in air had a lamella structure having a width of approximately 0.1 μm and comprised particles with a mixture of γ-Fe2O3and the Fe-poor spinel compound on their surfaces. Subsequent heating of this same material to 1373 K in air formed ε-Fe2O3in the particles. The crystallographic relationship between ε-Fe2O3and the modified spinel structure compound wasaε// [112̅]s,bε// [1̅10]s, andcε// [111]s(where ε and s indicate the ε-Fe2O3and spinel, respectively).