Abstract
The valence-band electronic structures of Zr-TM-Al (TM=Ni, Cu) bulk metallic glasses have been investigated by means of synchrotron-radiation photoelectron spectroscopy. Their valence-band spectra show Zr 4d-, Ni 3d- and Cu 3d-derived bands at the binding energies of 0.5, 2.0 and 3.6 eV, respectively. The Zr 4d-derived band becomes prominent around the excitation photon energy hν of 40 eV. It is found that the wider the supercooled liquid region ΔTx=Tx-Tg (Tx: the crystallization temperature, Tg: the glass transition temperature), the larger the peak binding energy of the Zr 4d-derived band becomes. For the photoexcitation at hν∼18 eV, where the Zr 4d states less contribute to the spectrum, the spectral intensity reduces towards the Fermi level. This may imply the formation of a pseudogap in the sp bands. It is also found that the width of the pseudogap for the occupied states becomes wider as ΔTx is increased. These spectral findings suggest that both the strength of the chemical bonding around Zr and the reduction in the electronic energy because of the pseudogap formation and the chemical bonding contribute to the large glass formation ability of the Zr-Cu-Al metallic glasses.
