Iron(II) carboxylato–hydrazinates: Ferrous fumarato–hydrazinate (FFH), FeC4H2O4.2N2H4; ferrous succinato–hydrazinate (FSH), FeC4H4O4.2N2H4;ferrous maleato–hydrazinate (FEH), FeC4H2O4.2N2H4;ferrous malato–hydrazinate (FLH), FeC4H4O5.2N2H4;ferrous malonato–hydrazinate (FMH), FeC3H2O4.1.5N2H4.H2O; and ferrous tartrato–hydrazinate (FTH), FeC4H4O6.N2H4.H2O are being synthesized for the first time. These decompose (autocatalytically) in an ordinary atmosphere to mainly 𝛾-Fe2O3, while the unhydrazinated iron(II) carboxylates in air yield 𝛼-Fe2O3, but the controlled atmosphere of moisture requires for the oxalates to stabilize the metastable 𝛾-Fe2O3. The hydrazine released during heating reacts with atmospheric oxygen liberating enormous energy, $$N_2H_4 + O_2 \rightarrow N_2 + H_2O;\Delta H_2O = – 621 kJ/mol,$$ which enables to oxidatively decompose the dehydrazinated complex to 𝛾-Fe2O3. The reaction products N2 + H2O provide the necessary atmosphere of moisture needed for the stabilization of the metastable oxide.
The synthesis, characterization and thermal decomposition (DTA/TG) of the iron(II) carboxylato–hydrazinates are discussed to explain the suitability of 𝛾-Fe2O3 in the ferrite synthesis.
Volume 42 | Issue 2