The manufacture and characterisation of aligned fibres of the ferroxplana ferrites Co2Z, 0.67% CaO-doped Co2Z, Co2Y and Co2W

Gel fibres of Co(2)Z, 0.67% CaO-doped Co(2)Z, Co2Y and Co2W ferrite were blow spun from an aqueous inorganic sol and collected as an aligned tow blanket, with an alignment comparable to that found in commercial fibres. The fibres were then heated to produce the desired ceramic phases, characterised by various techniques and their ferromagnetic resonance spectra measured. Single phase Co(2)Z was found by X-ray diffraction to form at a relatively low temperature of between 1200 degrees C and 1250 degrees C, and the material exhibited the expected microwave properties. Furthermore, an addition of 0.67% CaO was found to promote the formation of Co(2)Z at an even lower temperature of below 1200 degrees C and delay the exaggerated platy grain growth, which is normally encountered at the onset of formation of the Co(2)Z phase and which results in a mechanically weakened fibre. (C) 1998 Elsevier Science B.V. All rights reserved.