Structural study of glass coated Cu-based microwires

The microstructural characteristics of Cu based glass coated microwires are studied considering the different factors determined by their fabrication (composition and geometry), Two different sets of binary systems (CuxFe100- x and CuxCo100-x) and CU63Fe36P and Cu80Co19Ni samples have been studied. T he parameter that describes the geometry is the ratio p between the diamete r of the metallic nucleus and the external one corresponding to the layer o f the Pyrex glass. It straightforwardly relates to the fabrication process of the samples owing to the strong internal stresses in the samples because of the different thermal expansion coefficients of the glass coating and t he metallic nucleus. The structural study, carried out by means of wide ang le X-ray scattering (WAXS) and a subsequent identification of the crystalli ne peaks, reveals that Feet and Co phases coexist with a Cu phase in each s ystem. In the case of the samples containing P or Ni atoms, a third phase, Cu3P or Cu3.8Ni. respectively, appears. An evaluation of the relative conte nt of each phase shows in each system a sort of a master curve with a non-l inear p-dependence with a critical maximum at around rho = 0.25 for the Fe alpha and Co phases in the two systems. The calculation of the grain size s hows that nanocrystals around 40 nm in size are formed in all the cases by Fe alpha, Co and Cu phases. Magnetic measurements are now in progress in or der to complement these structural results. (C) 2001 Elsevier Science B.V. All rights