Magnetic properties of nanocrystalline CuFe2O4 and kinetics of thermal decomposition of precursor

Abstract

CuFe2(C2O4)3·4.5H2O was synthesized by solid-state reaction at low heat using CuSO4·5H2O, FeSO4·7H2O, and Na2C2O4 as raw materials. The spinel CuFe2O4 was obtained via calcining CuFe2(C2O4)3·4.5H2O above 400 °C in air. The CuFe2(C2O4)3·4.5H2O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform FT-IR, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and vibrating sample magnetometer. The result showed that CuFe2O4 obtained at 400 °C had a saturation magnetization of 33.5 emu g−1. The thermal process of CuFe2(C2O4)3·4.5H2O experienced three steps, which involved the dehydration of four and a half crystal water molecules at first, then decomposition of CuFe2(C2O4)3 into CuFe2O4 in air, and at last crystallization of CuFe2O4. Based on KAS equation, OFW equation, and their iterative equations, the values of the activation energy for the thermal process of CuFe2(C2O4)3·4.5H2O were determined to be 85 ± 23 and 107 ± 7 kJ mol−1 for the first and second thermal process steps, respectively. Dehydration of CuFe2(C2O4)3·4.5H2O is multistep reaction mechanisms. Decomposition of CuFe2(C2O4)3 into CuFe2O4 could be simple reaction mechanism, probable mechanism function integral form of thermal decomposition of CuFe2(C2O4)3 is determined to be 1 − (1 − α)1/4.