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

The synthesis of nano-crystalline CuFe2O4 powders by a combustion-like process isdescribed herein. Phase formation and evolution of the crystallite size during thedecomposition process of a (CuFe2)-precursor gel were monitored up to 1000 °C. Phase-purenano-sized CuFe2O4 powders were obtained after reaction at 750 °C for 2 h resulting in acrystallite size of 36 nm, which increases to 96 nm after calcining at 1000 °C. The activationenergy of the crystallite growth process was calculated as 389 kJ mol−1. The tetragonal -cubic phase transition occurs between 402 and 419 °C and the enthalpy change (dH) wasfound to range between 1020 and 1229 J mol−1 depending on the calcination temperature. The optical band gap depends on the calcination temperature and was found between 2.03 and1.89 eV. The shrinkage and sintering behaviour of compacted powders were examined. Denseceramic bodies can be obtained either after conventional sintering at 950 °C or after a twostepsintering process at 800 °C. Magnetic measurements of both powders and correspondingceramic bodies show that the saturation magnetization rises with increasing calcination-/sintering temperature up to 49.1 emu g−1 (2.1 μB f.u.−1), whereas the coercivity and remanencevalues decrease.