AN EXPERIMENTAL-STUDY ON THERMAL-DIFFUSIVITY OF NANOCRYSTALLINE AG

Thermal diffusivity (TD) and its relation to the microstructure of nan ocrystalline Ag (n-Ag), synthesized by inert-gas condensation and in-s itu compaction, was investigated by photoacoustic technique. The resul ts indicated that a dramatic decrease of TD in n-Ag (which is about 27 % that of p-Ag for the n-Ag with grain size 20 nm) is related to its s mall grain size and large volume fraction of interfacial component, an d originates mainly from reduction of its thermal conductivity. Anneal ing experiments showed that TD is not only affected by its grain size, but also strongly dependent on the microstructure of the interfaces. The increase of TD with increasing grain size can be explained by attr ibuting it mainly to the rise of effective electron density; while inc reasing TD by annealing where no substantial grain growth occurred, re flects an increase of electron transmission coefficient during anneali ng, which could also lead to a rise in effective electron density. In addition, the prompt decrease of TD with decreasing specimen density a s it is lower than 93% could be reasonably attributed to the increasin g number of extended boundaries in n-Ag.