Electronic Structure and Glass Formability in Metallic Glasses
- PDF / 276,022 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 23 Downloads / 222 Views
ELECTRONIC STRUCTURE AND GLASS FORMABILITY IN METALLIC GLASSES
R. HASEGAWA* AND K. TANAKA** * Nippon Amorphous Metals Co., Ltd, Kasumigaseki Bldg, Kasumigaseki, Chiyoda-ku, Tokyo 100 Japan and Allied-Signal Corporation, Morristown, NJ 07960*** **Nagoya Institute of Technology, Dept. of Metallurgical Eng., Showa-ku, Nagoya 466 Japan
ABSTRACT Recent developments in theory and experiment seem to enable us to relate the electronic structure to the formability of glassy states in Especially stressed is the role transition metal-metalloid base alloys. of the antibonding states in the glass formation.
INTRODUCTION The first attempt to relate electronic properties to glass stability in metallic glasses was made by Nagel and Tauc by using a nearly free electron They have argued that a glassy alloy is most stable when its model[l]. composition satisfies the condition that the wave number q. corresponding to the peak of the interference function is equal to the Fermi sphere diameter 2 kF, at which composition the density of states N(EF) becomes a minimum. Due to lack of pertinent experimental evidence, this proposal was neither Using the results of strongly rejected nor supported until around 1980. x-ray (XPS), ultra-violet (UPS) and Auger (AES) spectra on a glassy Pd-Si alloy, Riley et al have derived partial Pd 4d, Si 3p and Si 3s densities of states (PDOS) and concluded that the conduction band of the glassy alloy is far from free-electron-like and that the s-p portion of the density of states This is consistent near EF is a local maximum rather than a minimum [2]. with the low temperature specific heat data obtained for glassy Pd-Si-Cu The experimental situation involving glassy alloys by Mizutani et al [3]. For example, the electronic specific alloys containing Fe is less clear. heat coefficient y increases rapidly as the concentration of boron is The increase may be associated decreased in the glassy Fe-B system [4]. with the Invar-like properties of these alloys and is likely magnetic in origin. The XPS data of the same alloy system by Matsuura et al [5] and the XPS and UPS measurements on Fe-B and Fe-P-B by Amamou and Krill [6] These seem to be consistent with the PDOS calculations by Fujiwara [7]. calculations indicate a maximum of the DOS at EF and furthermore a splitting The latter feature is closely of the bonding and antibonding states. The relatively high Fermi level related to the present investigation. density of states thus appears to be one of the general properties of The free-electron model of transition metal base metallic glasses [8]. Nagel and Tauc [1], however, should be most applicable to non-transition A recent work by HAussler et al using XPS, metal base metallic glasses. UPS and AES on glassy Au-Sn, Ag-Sn and Cu-Sn shows that the stability against crystallization is a maximum at a composition at which the DOS at Although the situaEF is a minimum [9], being consistent with the model. tion is not clear at this moment, the experiment and the theory developed thus far indicate that detailed studies
Data Loading...
