Before its pressure treatment, the purity and structural features of the synthesized β-Fe2O3 sample were checked using conventional X-ray powder diffraction (XRD) and 57Fe Mössbauer spectroscopy. The room-temperature 57Fe Mössbauer spectrum of the β-Fe2O3 sample is well deconvoluted into three spectral components – two dominant doublets whose isomer shift and quadrupole splitting values are characteristic of the b-sites and d-sites in the β-Fe2O3 crystal lattice (with an ideal spectral ratio of 1:3 by the complete occupation of individual crystallographically non-equivalent cation positions by Fe3+). High-resolution transmission electron microscopy (HRTEM/TEM) images of the prepared β-Fe2O3 sample indicate that it contains nanoparticles of two distinct size classes (hereafter referred to as smaller and larger nanoparticle assemblies). It turns out that the two size fractions are well described (employing the χ2-test performed on a statistical level of confidence of 99%) in terms of lognormal distribution curves with average particle sizes of 15.6 and 52.3 nm and lognormal standard deviations of 0.34 and 0.41, respectively. Assuming that the density of β-Fe2O3 is irrespective of particle size within the sample and nanoparticles are more or less spherical, from the frequency vs. size distribution, the smaller and larger nanoparticle assemblies within the β-Fe2O3 sample account for 36.9(5) and 63.1(5) wt.%, respectively. The formation of the two-particle fractions is believed to be due to the solid-state reaction outlined in Eq. (1)45. This thermally-induced process occurs at a temperature of 400 °C, which is well below the decomposition temperature of iron(III) sulfate and the transition temperature for the transformation of β-Fe2O3 into α-Fe2O3 (~500 °C). However, the double sulfates formed by the reaction outlined in Eq. may also be transformed into β-Fe2O3. As such, two parallel processes of β-Fe2O3 formation – the primary reaction and the subsequent decomposition of the double sulfates – lead to the formation of the two-particle size fractions observed after the complete removal of all the sulfate-based by-products via dissolution in water. If you are looking for high quality, high purity, and cost-effective Iron oxide, or if you require the latest price, please feel free to email contact mis-asia.