No abstract

The structural parameters of nanoscale silver particles embedded in a silicate glass matrix have been determined by temperature-dependent EXAFS spectroscopy at the Ag K edge for two particle sizes of 2.5 and 6 nm. EXAFS measurements allowed us to probe both the oxygen environment of silver ions separated within the glass matrix and the structure of precipitated silver particles. The lattice parameter of the Ag particles showed an unusual dilatation of the silver structure that is a result of the glass cooling process. Furthermore, an increase was found of static and dynamic Debye-Waller factors as well as of the thermal expansion coefficient compared with bulk Ag material. The experiments demonstrate that the behaviour of metal particles incorporated into a glass matrix reflects size effects of nanoscaled particles and the influence of the surrounding matrix.

No abstract

No abstract

The thermal expansion behaviour of silver fcc has been described by an anharmonic Einstein model using EXAFS data in the temperature range between 10 and 300 K. The linear expansion coefficient of a bulk silver foil agrees well with X-ray diffraction data. In the case of silver particles embedded in a silicate glass matrix, this parameter shows an increase for particles of 3.2 nm in size by 70% whereas samples with an average size of particles of 5.1 nm show no changes compared with bulk fcc. The increase for small particles reflects the size effect as well as the influence of the surrounding matrix of glass. The results reveal a substantial influence of the distribution of particle sizes on the expansion coefficient.