The low temperature oxidation of the xZnFe
2O
4-(1-x)Fe
3O
4 solid solution in air was studied based on X-ray diffraction (XRD), magnetization and Mössbauer spectroscopy measurements. The phase separation on nanometer scale to the Zn-rich phase and Fe-rich phase begins in the samples with 0.25≤x≤0.80 during oxidation in air at 300°C. Following the increase in oxidizing time, the compositional fluctuation proceeds accompanied by the oxidation of Fe(II) ions to Fe(III) ions in the Fe-rich phase. The Fe-rich phase, in which undetectable Zn may exist, can be oxidized to γ-Fe
2O
3 after a long periods of oxidation at 300°C in air, because the separated Fe-rich phase has a nanometer size. Finally, we obtained the ZnFe
2O
4/γ-Fe
2O
3 nanocomposite. On the other hand, the precipitation of α-Fe
2O
3 occurs in the sample with x≤0.10 after the oxidation in air at 300°C. This may came from the fact that the separated Fe-rich phase is as large as the bulk Fe
3O
4 and the oxidation of Fe
3O
4 to γ-Fe
2O
3 can not take place after a certain period of annealing in air.
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