Observation of Fe3O4→α-Fe2O3 phase transformation at low temperature

1. Violeta Nikolic, University of Belgrade, Vinča Institute of Nuclear Sciences, Serbia, Serbia

The magnetic behavior of nanoparticles of magnetite coated with oleic acid (〖Fe〗_3 O_4/OA), synthesized by the hydrothermal method, was investigated in detail by SQUID measurements, performed by Nikolić et al. [1]. In order to get a better insight into the behavior of the prepared sample subjected to heat treatment, a more detailed thermo-gravimetric analysis was performed (thermal analyzer TA-SDT 2090). TG and DTA curves were measured by a standard protocol. Additional measurements of the sample dried under the lowered pressure were also performed. The results revealed that the processes, observed as a consequence of heat treatment, have a strong exothermic nature; the most intense DTA maximum is observed around T = 289 ° C. Having in mind the results of XRD and TEM analysis [1], as well as that the transformation of the magnetite phase into hematite represents an exothermic process: 〖Fe〗_3 O_4+1/4 O_2= 3/2 α-〖Fe〗_2 O_3+∆H, ∆H=115 kJ〖mol〗^(-1) [2,3], the observed exothermic process is attributed to 〖Fe〗_3 O_4→α-〖Fe〗_2 O_3 phase transformation at low temperatures (<300 ℃). The observed behavior could be ascribed to the presence of cation deficiency in the magnetite crystal lattice.
The author is gratefully acknowledged Dr N. Cvjetićanin for thermogravimetric measurements.

Ključne reči :

Tematska oblast: SIMPOZIJUM A - Nauka materije, kondenzovane materije i fizika čvrstog stanja

Datum: 13.03.2020.

Contemporary Materials 2020 - Savremeni Materijali

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