The synthesis of a monodisperse quaternary ferrite (FeCoCrO4) from the hot injection thermolysis of the single source precursor [CrCoFeO(O2CtBu)6(HO2CtBu)3]

Abstract

Monodisperse cobalt chromium ferrite (FeCoCrO₄) nanoparticles have been synthesised using the trimetallic pivalate cluster [CrCoFeO(O₂C^tBu)₆(HO₂C^tBu)₃]. The precursor was thermolysed in oleylamine and oleic acid, with diphenyl ether as the solvent at 260 °C. The effect of time and the concentration of the precursor on the stoichiometry of the phase formed and/or the morphology of the nanoparticles was studied. The reaction time was investigated by withdrawing aliquots at different times. No products were formed after 5 minutes and aliquots withdrawn at reaction times of less than 1 hour contain traces of iron oxide (Fe₂O₃); only cubic cobalt chromium ferrite (FeCoCrO₄) was obtained after one hour. Transmission Electron Microscopy (TEM) showed that more monodisperse spherical ferrite nanoparticles (4.0 ± 0.4 nm) were obtained at higher precursor concentrations. Magnetic measurements revealed that all the ferrite particles are superparamagnetic at room temperature but showed large hysteresis at low temperature. The nanoparticles were characterised by Powder X-Ray Diffraction (p-XRD) and Transmission Electron Microscopy (TEM). A Superconducting Quantum Interference Device (SQUID) was used to analyse the magnetic properties of the nanoparticles.