The synthesis and characterisation of Co2X (Ba2Co2Fe28O46) and Co2U (Ba4Co2Fe36O60) ferrite fibres, manufactured from a sol-gel process

The X and U phases of hexagonal ferrites are notoriously difficult to make as pure materials, and what little data there is published regarding their physical or magnetic properties relates only to single crystals. Stoichiometric Co2X and Co2U fibres were made from a sol-gel based process, and the characteristics of the sols and fibres were studied using PCS, XRD, SEM and VSM. The evolution of the X and U fibres was studied, and shown to be similar that of the W and Z fibres whose structures they respectively resemble. Co2X and Co2U had been formed at 1200°C, and the morphology of the fibres was different from those of the W and Z phases. The magnetic properties, again while resembling the W and Z phases, were different to any of the other hexagonal ferrite fibres. The magnetic hysteresis loops of both fibres were magnetically as was, the Co2X fibres having Ms = 45.0 emu g-1 and Hc = 0.085 T, and the Co2U fibres having Ms = 51.5 emu g-1 and Hc = 0.059 T. © 2001 Kluwer Academic Publishers.