Indian Journal of Pure & Applied Physics Vol. 44, February 2006, pp. 157-161 Crystallite size estimation of elemental and composite silver nano-powders using XRD principles Bharati R Rehani 1 , P B Joshi 1 , Kirit N Lad 2 & Arun Pratap 2 1 Department of Metallurgical Engineering Faculty of Technology & Engineering, The M S University of Baroda,Vadodara 390 001 2 Applied Physics Department, Faculty of Technology & Engineering, The M S University of Baroda,Vadodara 390 001 E-mail: apratapmsu@yahoo.com Received 25 May 2005; revised 8 November 2005; accepted 8 December 2005 Studies on nanocrystalline materials require an accurate determination of crystallite size as well as the microstrains induced in the material. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are the two well-known techniques for this purpose. Based on XRD principles, numerous approaches such as use of Scherrer equation, integral breath analysis, single-line approximation, Hall-Williamson method, etc have been developed for estimation of crystallite size. Present work deals with a systematic application of Hall-Williamson method for crystallite size estimation of high- energy milled elemental silver and silver-metal oxide (AgMeO) type composite powders and its comparison with Scherrer equation that does not take into account the peak broadening due to strain. The effect of second phase particles on the crystallite size of silver matrix in AgMeO composite is also investigated. Keywords: Crystal size, X-ray diffraction, Transmission electron microscopy IPC Code: G01N 1 Introduction Elemental silver and silver-base composites such as AgMeO composites are widely used for electrical applications as electrically conductive materials 1,2 . Apart from applications as contact materials in electrical switchgear devices like contactors, relays and switches, pure silver is also used as a filler material in conductive polymers 3 . It is well-known that altogether different combination of properties like electrical, electronic, optical, mechanical or chemical) is attainable with respect to bulk material if the grain size of the concerned material is in the nano- meter regime 4 . A multitude of physical and chemical synthesis techniques has been invented for the production of nanostructured materials in general and silver and its composites in particular 5-7 . High-energy milling or mechanical alloying (MA) is one such route that is gaining importance for synthesis of equiaxed (3D) nanostructured crystallites of silver-metal oxide composites such as Ag-CdO, Ag-SnO 2 , Ag-ZnO, Ag- In 2 O 3 , etc. for electrical contact applications over the years 8,9 . An accurate estimation of grain size/crystallite size becomes essential when such materials are produced with their crystallite size of the order of less than 100 nm. Though TEM is one of the powerful techniques for crystallite size measurement, it has certain limitations. Since TEM images represent only a local region, many samples and images are required to provide an average information for the entire sample. Not only this, the TEM sample preparation method is an involved and time consuming one. The XRD technique is free from these limitations. X-ray diffraction is, on the other hand, a simpler and easier approach for the determination of crystallite size of powder samples. The underlying principle for such a determination involves precise quantification of the broadening of the diffraction peaks. Based on this principle, a few techniques involving Scherrer equation, integral breath analysis or Hall-Williamson approach, Fourier method of Warren-Averbach, etc. have been developed 10-13 . Out of these options, the Hall-Williamson method of crystallite size estimation has been chosen in this investigation for determining the crystallite size of elemental silver and silver-cadmium oxide composite powders subjected to MA.