Study of the Electrical Resistivity Change upon Phase Transformation in Zr-Based Metallic Glass
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Study of the Electrical Resistivity Change upon Phase Transformation in Zr-Based Metallic Glass Keiko Komatsu, Ryuji Tamura, Shin Takeuchi, and Tadaharu Shibuya1 Dept of Materials Science and Technology, Science University of Tokyo, Noda, Chiba 278-8510, Japan 1 Faculty of Engineering, Toyo University, Kawagoe, Saitama 350-8585, Japan ABSTRACT In order to gain insight into the influences of formation of an icosahedral phase in Zr-based metallic glasses on the physical properties, thermal and electrical properties of Zr70Ni10Pd20 metallic glass were investigated. From DSC analyses, activation energies for the phase transition from an amorphous to an icosahedral phase and from the icosahedral to a crystalline (Zr2Ni) phase were estimated to be 3.42 and 3.07 eV, respectively. The effect of the phase transformations on the electrical resistivity was successfully observed; the resistivity clearly exhibits an increase and a decrease corresponding to the transitions from the amorphous to the icosahedral phase and from the icosahedral to the crystalline Zr2Ni phase, respectively. It is concluded that the increase of the resistivity upon the precipitation of the icosahedral phase is due to an increase of the volume fraction of the icosahedral grains, which possess higher resistivity. INTRODUCTION Since the first report on precipitation of an icosahedral phase from partially crystallized Zr-Al-Ni-Cu metallic glasses with high glass forming ability[1], it has been found that in many Zr-based multicomponent systems bulk metallic glasses are capable of forming an icosahedral phase at the earliest stage of crystallization. Substantial attentions have been paid to these metallic glasses since they are expected to provide us with some insights into the mechanism of nucleation and growth of the icosahedral phase and also into structural relationship between the icosahedral structure and the atomic configuration of Zr-based metallic glasses. Recently, Saida et al.[2] reported formation of an icosahedral phase as a primary precipitation phase in ternary metallic glasses such as Zr70Ni10M20(M=Pd, Au, Pt). In this paper, we report on studies of thermal and electrical properties of melt-spun Zr70Ni10Pd20 metallic glass. From the viewpoint of the physical properties it is also of great interest to study the influence L1.4.1
of such structural transitions on the electrical properties and to compare them among the three solid states; amorphous, quasicrystalline and crystalline state at the same composition. One of the peculiar properties of the icosahedral phase is very high resistivity and its large negative temperature dependence. Such high resistivity of the icosahedral phase is attributed to a combination of two effects: the presence of a pseudogap and localization tendency of conduction electrons at the Fermi level. The formation of the pseudogap is associated with observed strong Bragg reflections which satisfy KP=2kF, where KP and kF are the wave vector of the primary Bragg reflection and the Fermi wave vector, respectively. Theref
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