Crystallite-growth, phase transition, magnetic properties, and sintering behaviour of nano-CuFe{sub 2}O{sub 4} powders prepared by a combustion-like process

Journal Article · Thu May 01 00:00:00 EDT 2014 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2014.02.010· OSTI ID:22334200

Köferstein, Roberto ^[1]; Walther, Till ^[1]; Hesse, Dietrich ^[2]; Ebbinghaus, Stefan G. ^[1]

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1. Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120 Halle (Germany)
2. Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)

The synthesis of nano-crystalline CuFe{sub 2}O{sub 4} powders by a combustion-like process is described herein. Phase formation and evolution of the crystallite size during the decomposition process of a (CuFe{sub 2})—precursor gel were monitored up to 1000 °C. Phase-pure nano-sized CuFe{sub 2}O{sub 4} powders were obtained after reaction at 750 °C for 2 h resulting in a crystallite size of 36 nm, which increases to 96 nm after calcining at 1000 °C. The activation energy of the crystallite growth process was calculated as 389 kJ mol{sup −1}. The tetragonal⇄cubic phase transition occurs between 402 and 419 °C and the enthalpy change (ΔH) was found to range between 1020 and 1229 J mol{sup −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 °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 49.1 emu g{sup −1} (2.1 µ{sub B} fu{sup −1}), whereas the coercivity and remanence values decrease. - Graphical abstract: A cheap one-pot synthesis was developed to obtain CuFe{sub 2}O{sub 4} nano-powders with different crystallite sizes (36–96 nm). The optical band gaps, phase transition temperatures and enthalpies were determined depending on the particle size. The sintering behaviour of nano CuFe{sub 2}O{sub 4} was studied in different sintering procedures. The magnetic behaviour of the nano-powders as well as the corresponding ceramic bodies were investigated. - Highlights: • Eco-friendly and simple synthesis for nano CuFe{sub 2}O{sub 4} 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 CuFe{sub 2}O{sub 4}. • Magnetic behaviour of CuFe{sub 2}O{sub 4} powders and ceramics depending on their particle size.

• OSTI ID: 22334200
• Journal Information: Journal of Solid State Chemistry, Vol. 213; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
CALCINATION
CERAMICS
COERCIVE FORCE
ENTHALPY
FERRITE
FERRITES
MAGNETIC PROPERTIES
MAGNETIZATION
MONITORING
NANOSTRUCTURES
PARTICLE SIZE
PHASE TRANSFORMATIONS
POLYMERIZATION
POWDERS
SINTERING
SPINELS
SYNTHESIS
TRANSITION TEMPERATURE