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Abstract
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The CuxFe3?xO4(0.75 ? x ? 1.25) nano-crystalline powders were prepared by an optimized glycine-nitrate process (GNP) followed by calcination. Thermal analysis and X-ray diffraction (XRD) data revealed that formation of CuFe2O4 takes place in three steps. In the first step, iron and copper nitrates decompose toFe2O3and Cu, respectively. Then, Cu changes to CuO and finally CuO reacts with Fe2O3to form CuFe2O4.The optimized GNP process was then applied on CuxFe3?xO4 spinels to find the optimum x value representing a single phase product with the best conductivity. Electrical measurements in air at 650–800?C showed that the highest electrical conductivity, among CuxFe3?xO4spinels, belonged to stoichiometricCuFe2O4compound (7.6 S cm?1with 1.5% uncertainty at 800?C). The results of annealing exhibited that the resulting CuFe2O4spinel is thermally stable and its crystallite growth behavior can be explained by the parabolic grain growth law. The activation energy of the crystallite growth was calculated as 363 kJ mol?1 with 4% uncertainty.
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