Electrical Resistivity and Structural Changes Upon Relaxation and Crystallization of (Mo/sub 0.6/Ru/sub 0.4/)sub 100-X/B/sub X/ Metallic Glasses

摘要

Crystalliztion of (Mo/sub 0.6/Ru/sub 0.4/)/sub 100-x/B/sub x/ glasses takes place in three steps. The first step, corresponds to the precipitation of the sigma phase Mo sub 5 Ru sub 3 which decomposes at higher temperatures. The second step is associated with the formation of an hcp solid solution of Mo in Ru, and in the last step the remaining amorphous matrix crystallize in an fcc boride. Detailed electrical resistivity measurements taken below the crystallization temperature reveal an excess resistivity above the usual linear temperature dependence predicted by the Ziman theory. The increase in resistivity is associated with the onset of long range compositional inhomogeneity (spinodal decomposition) and the decrease with the beginning of crystallization. The electrical behavior for samples pre-annealed for 12 hours at various temperatures suggest that boron migration is partly responsible for this excess resistivity. The linear relationship between the conductivity and the electronic density of states across the concentration range, and the fact that upon annealing (Mo/sub 0.6/Ru/sub 0.4/) sub 82 B sub 18 the maximum in the excess resistivity is associated with a minimum in the density of states, indicates that Mott's model is not applicable and suggests that the d electrons are important in the conduction. The changes in the radial distribution function during annealing at 525 degrees C are also reported. (ERA citation 09:046184)