Recent study of nanomaterials prepared by inert gas condensation using ultra high vacuum chamber

摘要

The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline materials such as PbF_2, Mn~(2+)-doped PbF_2, Sn-doped In_2O_3 (ITO), ZnO, Al_2O_3, Ag_2O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and character-ized. Results of some of these materials will be presented in this paper. In solid-state ~(207)Pb NMR on PbF_2 a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease in grain size. Presence of electronic centres in nanocrystalline PbF_2 is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al_2O_3 was prepared and ~(56)Fe ions were implanted. After implantation segregation of ~(56)Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O_2 atmosphere. The growth of ITO under O_2 atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied.