MICROSTRUCTURAL INVESTIGATION OF COLLOIDAL SILVER EMBEDDED IN GLASS

Nanoparticulate composites consisting of very small silver particles embedded in near-surface regions of glass were obtained by sodium-silver ion exchange, Colloidal silver is formed by reduction of silver ions and aggregation of silver atoms in the glass matrix at elevated temperatures. Owing to absorption bands in the visible region, the silver particles cause a coloration of the glass that depends on their size and depth distribution. From high-resolution electron microscopy imaging of lattice plane fringes of the silver particles, size-dependent lattice contractions are deduced that are larger than those reported in the literature for supported particles not interacting with a matrix. This 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.