Analyzes of glasses of Ge-Se-Ag system employing synchrotron radiation and complementary techniques

CONDE GARRIDO, J. M.; ERAZU, M.; ROCCA, J.; FONTANA, M.; MARIA ANDREA UREÑA; ARCONDO, B.

Campinas, Brasil

Conferencia; 6 International Conference on Synchroton Radiation in Materials Science; 2008

LNLS

GexSe1-x system is an easy glass former for x < 0.43 atomic fraction. The glasses are covalently bonded and the connectivity and other properties of the network are strongly dependent on composition. This network structure presents the so called intermediate range order (IRO) which manifestation is a first sharp diffraction peak (FSDP) of the total structure factor S(q), observed at q ≈ 1Å-1.GexSe1-x glasses are described as floppy for x < 0.20 and rigid for x > 0.26 whereas an intermediate stress free phase is proposed in between [Boolchand 01, Boolchand 02]. Due to this feature, the glass forming tendency is not substantially affected by the addition of metals to GexSe1-x base alloy, in the intermediate phase composition range,  whereas they impact outstandingly on electric, magnetic and optic properties.My(GexSe1-x)1-y glasses, with M=Ag, Cu, Fe or their combination and were obtained as bulk glasses by the melt quenching technique and, as films, by pulsed laser deposition (PLD). Ag and Cu addition, above a threshold concentration, turn over the semiconductor nature of GexSe1-x glasses to a fast ionic behavior. On the other hand, the addition of a small quantity of Fe confers the glasses very peculiar magnetic behavior.Scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS) were employed to analyze homogeneity in these glasses.  X-ray diffractometry (XRD) and Mössbauer spectroscopy were used in structure studies. XAFS was employed to characterize the local environment of the different atoms. Magnetic moment were measured as a function of temperature and magnetic field for Fe containing glasses. Finally, electric and magnetic behavior is analyzed as a function of structure, composition and local order in these glasses.