Investigation of stress state of silver nanoparticles in silicate glasses by means of EXAFS

Abstract

Nanosized spherical silver particles were formed in silicate glass by sodium/silver ion exchange and subsequent annealing in air or hydrogen atmosphere at elevated temperatures. Furthermore, the sol-gel procedure was used to prepare embedded Ag particles. Structural characterisation of these composite materials by temperature dependent EXAFS-spectroscopy with transmission and fluorescence experiments revealed distinct differences of the particle/matrix interaction across the interface. The Ag-O and Ag-Ag correlations could be separated by fit procedures. The Ag-Ag bond length of the crystalline particles sensitively reflects their state of stress depending on the formation conditions. It was found an increase as well as a decrease of the Ag-Ag distance, i. e. tensile and compressive stress states were formed, for ion-exchanged glasses as a result of different cooling procedures and after hydrogen treatments, respectively, and for sol-gel samples. The combination with high-resolution electron microscopy (HREM) experiments yields the confirmation of such effects. Furthermore, the size-dependent parameters of nanoparticles could be determined. The results can be interpreted by the size effect of nanoscaled particles and the influence of the surrounding matrix.