Crystallite-growth, phase transition, magnetic properties, and sintering behaviour of nano-CuFe2O4 powders prepared by a combustion-like process

The synthesis of nano-crystalline CuFe2O4 powders by a combustion-like process is described herein. Phase formation and evolution of the crystallite size during the decomposition process of a (CuFe2)-precursor gel were monitored up to 1000 degrees C. Phase-pure nano-sized CuFe2O4 powders were obtained after reaction at 750 degrees C for 2 h resulting in a crystallite size of 36 nm, which increases to 96 nm after calcining at 1000 degrees C. The activation energy of the crystallite growth process was calculated as 389 kJ mol(-1). The tetragonal(sic)cubic phase transition occurs between 402 and 419 degrees C and the enthalpy change (Delta H) was found to range between 1020 and 1229J mol(-1) depending on the calcination temperature. The optical band gap depends on the calcination temperature and was found between 2.03 and 1.89 eV. The shrinkage and sintering behaviour of compacted powders were examined. Dense ceramic bodies can be obtained either after conventional sintering at 950 degrees C or after a two-step sintering process at 800 degrees C. Magnetic measurements of both powders and corresponding ceramic bodies show that the saturation magnetization rises with increasing calcination-/sintering temperature up to 49.1 emu g(-1) (2.1 mu(B) fu(-1)), whereas the coercivity and remanence values decrease. (C) 2014 Elsevier Inc. All rights reserved.