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°C. Phase-pure nano-sized CuFe2O4 powders were obtained after reaction at 750°C for 2h resulting in a crystallite size of 36nm, which increases to 96nm after calcining at 1000°C. The activation energy of the crystallite growth process was calculated as 389kJmol−1. The tetragonal⇄cubic phase transition occurs between 402 and 419°C and the enthalpy change (ΔH) was found to range between 1020 and 1229Jmol−1 depending on the calcination temperature. The optical band gap depends on the calcination temperature and was found between 2.03 and 1.89eV. The shrinkage and sintering behaviour of compacted powders were examined. Dense ceramic bodies can be obtained either after conventional sintering at 950°C or after a two-step sintering process at 800°C. Magnetic measurements of both powders and corresponding ceramic bodies show that the saturation magnetization rises with increasing calcination-/sintering temperature up to 49.1emug−1 (2.1µBfu−1), whereas the coercivity and remanence values decrease. A cheap one-pot synthesis was developed to obtain CuFe2O4 nano-powders with different crystallite sizes (36–96nm). The optical band gaps, phase transition temperatures and enthalpies were determined depending on the particle size. The sintering behaviour of nano CuFe2O4 was studied in different sintering procedures. The magnetic behaviour of the nano-powders as well as the corresponding ceramic bodies were investigated. [Display omitted] •Eco-friendly and simple synthesis for nano CuFe2O4 powder using starch as polymerization agent.•Monitoring the phase evolution and crystallite growth kinetics during the synthesis.•Determination of the optical band gap, phase transition temperature, and enthalpy change.•Sintering behaviour of nano-sizes CuFe2O4.•Magnetic behaviour of CuFe2O4 powders and ceramics depending on their particle size.