EVOLUTION OF THE ELECTRICAL-RESISTIVITY DURING THE CRYSTALLIZATION OFCO-SI-B GLASSES

The thermal variation of the resistivity during the crystallization pr ocess has been recorded and compared to differential scanning calorime try, X-ray diffraction, and neutron thermodiffractometry over a wide c omposition range covering most of the amorphization range, giving comp lementary information about the different steps of crystallization as well as morphological and topological changes, and size and shape of t he crystallites. The usefulness of the analysis of data considering al l these technique together is discussed. Primary crystallization, with excess of Co content in a first step, takes place in Co-rich compound s. In Co-poor Si-rich alloys, the crystallization follows an eutectic behavior with the precipitation of Co2Si, Co2B, and Co(Fm3m and P6(3)/ mmc), progressively growing in size. At the end of the process, the sa me final products are detected for the whole composition range. Anomal ous cases with an increase of resistivity at the onset of the crystall ization process, reminiscent of those found in nanocrystalline Fe-Nd-C u-Si-B alloys, have been found in some compounds such as Co70Si9B21 an d Co71Si17.5B11.5.