Evolution of the Electrical Resistivity during the Crystallization of Co-Si-B Glasses

Abstract

The thermal variation of the resistivity during the crystallization process has been recorded and compared to differential scanning calorimetry, X-ray diffraction, and neutron thermodiffractometry over a wide composition range covering most of the amorphization range, giving complementary information about the different steps of crystallization as well as morphological and topological changes, and size and shape of the crystallites. The usefulness of the analysis of data considering all these technique together is discussed. Primary crystallization, with excess of Co content in a first step, takes place in Co-rich compounds. In Co-poor Si-rich alloys, the crystallization follows an eutectic behavior with the precipitation of Co2Si, Co2B, and Co(Fm3m and P63/mmc), progressively growing in size. At the end of the process, the same final products are detected for the whole composition range. Anomalous cases with an increase of resistivity at the onset of the crystallization process, reminiscent of those found in nanocrystalline Fe-Nd-Cu-Si-B alloys, have been found in some compounds such as Co70Si9B21 and Co71Si17.5B11.5.