MICROSTRUCTURAL INVESTIGATION OF COLLOIDAL SILVER EMBEDDED IN GLASS

Nanoparticulate composites consisting of very small silver particles e mbedded in near-surface regions of glass were obtained by sodium-silve r ion exchange, Colloidal silver is formed by reduction of silver ions and aggregation of silver atoms in the glass matrix at elevated tempe ratures. Owing to absorption bands in the visible region, the silver p articles cause a coloration of the glass that depends on their size an d depth distribution. From high-resolution electron microscopy imaging of lattice plane fringes of the silver particles, size-dependent latt ice contractions are deduced that are larger than those reported in th e literature for supported particles not interacting with a matrix. Th is effect is the more pronounced the higher the annealing temperature is during the particle formation. The increased lattice contraction is attributed to compressive stresses that arise during the ion exchange process as well as during cooling after annealing.