PD-TI BIMETALLICS - A STUDY OF THE ELECTRONIC-STRUCTURE USING X-RAY PHOTOELECTRON-SPECTROSCOPY AND X-RAY-ABSORPTION NEAR-EDGE STRUCTURE

We studied the core-level binding-energy shifts and the valence-band b ehavior of Pd3Ti and PdTi2 alloys using x-ray photoelectron spectrosco py (XPS) and x-ray-absorption near-edge structure (XANES). The observe d Pd core-level shifts in the alloys, relative to the pure metal, were not consistent with the electronegativity predictions. It is proposed that upon alloying there is an increase in the number of sp-like cond uction electrons and a decrease in the number of d electrons at the Pd site. This electron redistribution at the noble-metal site in the all oy results in a small net charge flow between Pd and Ti, in the direct ion in accord with electronegativity predictions. Pd L3-edge and Ti K- edge XANES provide further evidence of electron redistribution upon al loying. Net charge transfer at the Pd site of PdTi2 has been estimated to be 0.29+/-0.02 electron counts on the basis of a charge compensati on model, results from XPS binding-energy shift, and XANES white-line areas. The observed Pd valence-band narrowing and shifts to a higher b inding energy are also explained in terms of dilution and charge redis tribution.