The formation and characterization of silver clusters in zirconia

Silver clusters with size ranging from a few nanometers to several nanometers are formed in zirconia matrix and have been characterized by low frequency Raman scattering (LFRS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies. Surface acoustic vibrational modes of the Ag nanoclusters are observed in the LFRS measurements and the estimated size of silver clusters is of the order of a few nm. XRD measurements indicate the presence of silver clusters in the matrix having a mean size of 20 nm. TEM observations on the zirconia powder indicate the presence of silver clusters as deduced by selected area diffraction pattern analysis. The microscopic structure of the reference ZrO2 sample indicates oxygen related disorder which might act as the heterogeneous nucleating centers of silver clusters as studied by time differential perturbed angular correlation. Based on the experimental results in the present study, it is proposed that the diffusion of Ag atoms through grain boundaries and pore walls could be the dominant mechanism leading to the formation of Ag clusters in the zirconia matrix.