Synthesis of natural superlattice structure in the binary ZnO–Fe₂O₃ system by microwave irradiation

Abstract

Homologous compounds, Fe 2 O 3 (ZnO) m , with the modulated natural superlattice structure were obtained within a short period by solid state reaction of component oxides under 2.45 GHz microwave irradiation. TEM observation revealed that two types of superlattice structures were observed in different Fe concentration; one is longitudinal superlattice structure in a rod shaped precipitation at high Fe concentration, and the other is modulated structure showing zigzag shape at low Fe concentration. It is conclude that the non-equilibrium nature of microwave selective heating, as well as rapid heating and quenching effects, plays a key role to form the superstructure. The obtained products exhibit ferromagnetic behavior with the Curie temperature above 300 K.

Synthesis of homologous compounds Fe2O3(ZnO) (m=6, 8, 34) by various selective microwave heating conditions

“…The existence of satellite spots indicated that the rod has a modulated wurtzite-type structure. These results are consistent with an existing study [18]. The TEM observations confirmed that the rod-shaped structure consisted of homologous compounds, Fe 2 O 3 (ZnO) m , and the wurtzite-type phase observed in the XRD pattern corresponded to these homologous compounds.…”

“…6a), revealed a zigzag shape in each layer. The zigzag structure of Fe 2 O 3 (ZnO) m was similar to the structure observed in previous studies [16,18]. It is known that the appearance of the zigzag structure is related to the value of m, i.e., the Fe/Zn ratio [34].…”

“…Previous studies have shown that structures that could not be synthesized by conventional heating were synthesized by microwave irradiation [18][19][20]. Microwave heating has drawn attention as a material synthesis technique and has been used in diverse ways [21][22][23][24][25].…”

Structure and magnetic properties of FeAl2O4 synthesized by microwave magnetic field irradiation

“…In the 1990s, it began to be reported that microwave processes differ from processes that do not use microwaves. For example, microwaves can create supersaturated solid solutions, enhancement of sintering, changes in the materials structure, and so on [6][7][8]. These phenomena are well known as "microwave effects.…”

Survey of new materials by solid state synthesis under external fields: high-pressure synthesis and microwave processing of inorganic materials

“…In addition, we also observed a formation of natural superlattice structure of Fe 2 O 3 (ZnO) m homologous compounds. 58) Important fact is that these materials were synthesized by a simple procedure, only MW irradiation to the powder mixture of ZnO and £-Fe 2 O 3 , suggesting the following mechanism of the reaction. When MWs are irradiated to the powder mixture, rapid heating is achieved by strong coupling with MW energy.…”