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

Abstract

The structure and magnetic properties of FeAl 2 O 4 synthesized by microwave magnetic field (H-field) irradiation were investigated to reveal the effect of the H-field on the crystal structure and the magnetic characteristics of an antiferromagnetic material. The role of the H-field was investigated using a singlemode cavity, which can spatially separate the maximum points of the alternating electric field (E-field) and H-field in the cavity. In H-field irradiation, the crystallite diameter decreased compared to that in conventional heating. In conventional heating, the crystallite diameter did not change with increasing quenching speed. Thus, it is suggested that a decrease in crystallite diameter occurs during H-field irradiation. Furthermore, magnetization after H-field irradiation was greater than that after conventional heating. It is considered that magnetic clusters appear when Fe 3+ partially replaces Al 3+ in the octahedral sites in the grain boundaries, which were formed as a result of decreasing crystallite diameter.

Pristine and Al-doped hematite printed films as photoanodes of p-type dye-sensitized solar cells

“…As shown in Table 1, mixtures B, C, and D led to the production of oxides with different Al-content. The Al/ Fe mass ratio, determined through photometry measurements, showed values close to those calculated considering the composition of mixtures A, B, C, and D. Since XRD patterns have shown the presence of AlFe 2 O 4 (hercynite), it is important to consider that in this phase, iron is present as both Fe 2+ and Fe 3+ (Fukushima et al Takizawa 2013;Jastrzębska et al 2015). Thus, the addition of concentrated H 2 O 2 became compulsory in order to precisely quantify the real amount of iron in the samples, as the photometric method is specific solely for Fe 3+ .…”

“…When Al (acac) 3 was added into precursor mixture, the XRD patterns of the powders obtained by thermal degradation indicated the existence of a second crystal phase. Three new peaks at 30.4°, 43.5°, and 63.1°were assigned, respectively, to (220), (400), and (440) planes of AlFe 2 O 4 (hercynite JCPDS 007-0068) (Fukushima et al 2013;Jastrzębska et al 2015). The peak at 57.5 can be assigned to both α-Fe 2 O 3 and AlFe 2 O 4 .…”

Efectos del contenido de CaCO3 inicial en las propiedades magnéticas de sedimentos calcinados. Resultados preliminares

“…Una explicación del comportamiento observado es que durante el proceso de descarbonatación (a partir de los 800 ºC) y formación de silicatos cálcicos, se produzcan localmente, condiciones que conllevan a la reducción del estado de oxidación del hierro y la consecuente formación de minerales ferrimagnéticos, fenómeno que siguiendo a Jordanova y Jordanova (2016) podría vincularse acción de los gases liberados (CO/CO 2 ). Cabe destacar que en los difractogramas expuestos en Cultrone et al (2001) (Dutta y Sharma, 2011, Fukushima et al, 2013, la presencia de fases correspondientes a la solución sólida magnetita-hercinita resulta factible teniendo en cuenta las concentraciones relativamente elevadas de aluminio (Al 2 O 3 ) en las muestras tratadas; esto es sin duda un motivo de análisis para futuras contribuciones. Por otro lado Bidegain et al (2010), en un estudio sobre polución por carbón de coque en la localidad de Ensenada (Argentina), indicaron que durante el proceso de producción, en el horno de la fábrica, se forman nano-esferas magnéti-cas cuya composición química es dominada por hierro (97 %) y el porcentaje de oxígeno es muy bajo (alrededor de 3 %), es decir, se aproximan al αFe (ferromagnético).…”

Distribution of Clay Minerals in Light Coal Fractions and the Thermal Reaction Products of These Clay Minerals during Combustion in a Drop Tube Furnace

“…By searching the XRD phase database PDF2004, this new mineral was determined to be a zinc-bearing hercynite with the chemical formula Zn0.4Fe0.6Al2O4, based on the relationship between the structural parameters and the Fe-to-Zn ratio provided by Waerenborgh et al [36]. Since hercynite has a high melting point of 1740 °C [37], the new mineral also has a high melting point. The production of this mineral proves that zinc oxide was involved in clay mineral reactions during DTF combustion of the SH light coal.…”