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Li 0.5 x Mn 0.4 Ni 0.6– x Fe 2+0.5 x O 4 (0.0≤ x ≤0.3) was obtained by calcining oxalates precursor over 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. A high-crystallized Li 0.5 x Mn 0.4 Ni 0.6– x Fe 2+0.5 x O 4 with a cubic structure was obtained when the precursor was calcined at 600 °C in air for 2 h. The specific saturation magnetization of Li 0.5 x Mn 0.4 Ni 0.6– x Fe 2+0.5 x O 4 depends on the composition and calcination temperature. Li 0.1 Mn 0.4 Ni 0.4 Fe 2.1 O 4 obtained at 600 °C had the highest specific saturation magnetization value, 57.94 emu/g. However, Mn 0.4 Ni 0.6 Fe 2 O 4 obtained at 600 °C had the highest coercivity value, 130.32 Oe.

Co1−xMgxFe2O4 precursor was synthesized by solid-state reaction at low temperatures using MgSO4·7H2O, CoSO4·7H2O, FeSO4·7H2O, and Na2C2O4 as raw materials. Co1−xMgxFe2O4 was obtained by calcining the precursor over 500 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometry. A high-crystallized Co1−xMgxFe2O4 with a cubic structure was obtained when the precursor was calcined at 500 °C in air for 2 h. The specific saturation magnetizations of Co1−xMgxFe2O4 depend on the calcination temperature and composition. The thermal transformation of the precursor from ambient temperature to 850 °C in air presented two steps. The values of the activation energies associated with the thermal transformation of CoC2O4–2FeC2O4·5.77H2O were determined based on the KAS equation.

Nd 2 O 3 was synthesized by calcining Nd 2 (C 2 O 4 ) 3 ·10H 2 O in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, and scanning electron microscopy. The results showed that high-crystallized Nd 2 O 3 with hexagonal structure was obtained when the precursor was calcined at 1223 K in air for 2 h. The crystallite size of Nd 2 O 3 synthesized at 1223 K for 2 h was about 48 nm. The thermal decomposition of the precursor in air experienced three steps, which are first, the dehydration of 10 crystal water molecules; then, the decomposition of Nd 2 (C 2 O 4 ) 3 into Nd 2 O 2 CO 3 ; and last, the decomposition of Nd 2 O 2 CO 3 into hexagonal Nd 2 O 3 . Based on the KAS equation, the values of the activation energies associated with the thermal decomposition of Nd 2 (C 2 O 4 ) 3 ∙10H 2 O were determined.