Thermal decomposition of almandine garnet: Mössbauer study
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The thermal decomposition of almandine garnet from Zoltye Vody, Ukraine, has been studied using57Fe Mössbauer spectroscopy. Room temperature Mössbauer spectrum of the initial powdered sample is characterised by one doublet corresponding to Fe2+ in dodecahedral position 24c. In the room temperature spectra of all heated almandine samples, a doublet corresponding to γ-Fe2O3 nanoparticles appeared. Depending on experimental conditions (heating temperature and time), the additional spectral lines of α-Fe2O3 and ε-Fe2O3 were observed in Mössbauer spectra.
It is obvious that the thermal transformation of almandine garnet in air is related to the primary formation of γ-Fe2O3 superparamagnetic nanoparticles. γ-Fe2O3 nanoparticles are transformed into ε-Fe2O3 and consequently into α-Fe2O3 at higher temperatures. The mechanism and kinetics of the individual structural transformations depend on experimental conditions — mainly on the heating temperature and size of the particles.
KeywordsHyperfine Magnetic Field Hyperfine Parameter Almandine Akaganeite Superparamagnetic Nanoparticles
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