Synthesis and Characterization of Co-Zn Ferrite Nanocrystals for Magnetocaloric Applications
S. Urcia-Romero, B. Renteria, O. Perales-Pérez, G. Gutiérrez
University of Puerto Rico, PR
Keywords: nanoparticles, synthesis, ferrite, magnetocaloric effect
Abstract:Cobalt ferrite (CoFe2O4) is known for its high coercivity, chemical stability and high sensitivity of its Curie temperature (TC) with Zn-doping. A ferrofluid bearing this type of ferrite nanocrystals could be then considered good candidate for magnetocaloric energy conversion applications. Accordingly, the present work addresses the synthesis and magnetic characterization of CoxZn1-xFe2O4 nanoparticles in the ‘x’ range between 0.5 and 1.0. Ferrite nanocrystals were synthesized by conventional coprecipitation method as well as through a modified size-controlled approach where the mixture of reactants was carried out at selected flow-rates. X-ray diffraction analyses confirmed the formation of the ferrite structure in the evaluated composition interval. The average ferrite crystallite size synthesized in the ‘x’=0.5-1.0 range varied from 8.8 nm to 16.2 nm (with no control on flow-rate) and from 9.5 nm to 18.7 nm, when the reactants were mixed at 20mL/min. The magnetization at 2.2T was as high as 63 emu/g (‘x’=0.8) whereas the coercivity varied from 8 Gauss to 334 Gauss with a rising ‘x’. The magnetization and coercivity varied from 31 emu/g to 63 emu/g and 22.9 Gauss to 976 Gauss when the solids were produced at 20mL/min within the same ‘x’ range.