Structural study of glass coated Cu-based microwires

Abstract

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 (Cu x Fe 100− x and Cu x Co 100− x ) and Cu 63Fe 36P and Cu 80Co 19Ni samples have been studied. The parameter that describes the geometry is the ratio ρ between the diameter of the metallic nucleus and the external one corresponding to the layer of 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 the metallic nucleus. The structural study, carried out by means of wide angle X-ray scattering (WAXS) and a subsequent identification of the crystalline peaks, reveals that Feα and Co phases coexist with a Cu phase in each system. In the case of the samples containing P or Ni atoms, a third phase, Cu 3P or Cu 3.8Ni, respectively, appears. An evaluation of the relative content of each phase shows in each system a sort of a master curve with a non-linear ρ-dependence with a critical maximum at around ρ=0.25 for the Feα and Co phases in the two systems. The calculation of the grain size shows that nanocrystals around 40 nm in size are formed in all the cases by Feα, Co and Cu phases. Magnetic measurements are now in progress in order to complement these structural results.