Molecular Level Synthesis of InFeO₃ and InFeO₃/Fe₂O₃ Nanocomposites

Abstract

New heterometallic In−Fe alkoxides [InFe-(O t Bu) 4 (PyTFP) 2 ] (1), [InFe 2 (O neo Pen) 9 (Py)] (2), and [In-Fe 3 (O neo Pen) 12 ](3) were synthesized and structurally characterized. The arrangement of metal centers in mixed-metal framework was governed by the In:Fe ratio and the coordination preferences of Fe(III) and In(III) centers to be in tetrahedral and octahedral environments, respectively. 3 displayed a star-shaped socalled "Mitsubishi" motif with the central In atom coordinated with three tetrahedral {Fe(O neo Pen) 4 } − anionic units. The deterministic structural influence of the larger In atom was evident in 1 and 2 which displayed the coordination of neutral coligands to achieve the desired coordination number. Thermal decomposition studies of compounds 1−3 under inert conditions with subsequent powder diffraction studies revealed the formation of Fe 2 O 3 and In 2 O 3 in the case of 3 and 2, whereas 1 intriguingly produced elemental In and Fe. In contrary, the thermal decomposition of 1−3 under ambient conditions produced a ternary oxide, InFeO 3 , with additional Fe 2 O 3 present as a secondary phase in a different stoichiometric ratio predetermined through the In:Fe ratio in 2 and 3. The intimate mixing of different phases in InFeO 3 /Fe 2 O 3 nanocomposites was confirmed by transmission electron microscopy of solid residues obtained after the decomposition of 1 and 2. The pure InFeO 3 particles demonstrated ferromagnetic anomalies around 170 K as determined by temperature-dependent fieldcooled and zero-field-cooled magnetization experiments. A first-order magnetic transition with an increase in the ZFC measurements was explained by temperature-induced reduction of the Fe−Fe distance and the corresponding increase in superexchange.

Controlling Degree of Inversion in MgFe2O4 Spinel Films Grown in External Magnetic Fields

“…Thermogravimetric analysis (TG) of 1 (Figure 3a) indicated instant hydrolysis of the precursor in the initial phase which is common in metal alkoxides, which demonstrates their intrinsically high reactivity, making them attractive precursors for metal oxides. [30][31][32][33][34] The three-step decomposition led to a total mass loss of 69% (7.327 mg of 10.6189 mg) (Δm 1 = 64% (6.796 mg) in the range 25-260 °C, Δm 2 = 4% (0.425 mg) in the range 260-500 °C, and Δm 3 = 1% (0.106 mg) in the range 500-900 °C) that is close to the theoretical mass loss of 72% expected for the formation of MgFe 2 O 4 . The deviation in the weight loss is possible due to the initial hydrolysis, which is inevitable despite the precursor handling in dry nitrogen, of the sample.…”