NUCLEAR TECHNIQUES CHARACTERIZATION OF SHORT-RANGE ORDER IN

L. C. DAMONTE

Annales Chimie Science deux Materials

Elsevier

Lugar: Paris; Año: 2002 vol. 27 p. 61 - 67

- In this paper an overview of recent and new perturbed angular correlation (PAC), MSssbauer (MS) and positron annihilation (PAS) experiments on Zr- and Hf-based bulk metallic glasses is presented. PAC results showed that all samples in their as-prepared amorphous state, irrespective of the preparation method used, are well described by a dense random packing of ions (DRP). Hf-based samples showed a greater electric field gradient (EFG) value than Zr-based ones for same composition. A general observation is that the relaxed amorphous and supercooled liquid has the same local arrangements than the initial amorphous state. The crystallization behaviour is not preparation-method dependant but composition and impurities have a major influence on it. Preliminary positron annihilation lifetime measurements on amorphous samples yielded one characteristic lifetime, with a value intermediate between those for the well-annealed and defected metallic constituents of the alloys. M6ssbauer spectra of as-prepared amorphous alloys consist of a broad asymmetric doublet, originating from a distribution of electric field gradients characteristic for amorphous samples.