Mechanosynthesis and mechanical activation processes to the preparation of the Sr2[Sn-1TinO3n+1] Ruddlesden-Popper family

A novel mechanochemical activation route has been applied in order to obtain the n = 1-4 and infinity members of the Sr-2[Sr(n-1)TinO(3n+1)] Ruddlesden-Popper series. The evolution of the (n + 1)SrO:nTiO(2) powder mixtures during mechanical treatment was followed by X-ray powder diffraction in all cases. Except for the 2SrO:TiO2 composition, SrTiO3 was always mechanosynthesized. High-energy nailling of 2SrO:TiO2 sample resulted in the formation of nanosizcd Sr2TiO4, which is the only K2NiF4-type oxide prepared by mechanical treatment until now. The mechanical treatment was followed by annealing at different temperatures to establish the optimized protocol for synthesis of each member of the series. SrTiO3, Sr2TiO4 and Sr3Ti2O7 were obtained with very important decreases in the formation temperatures and reaction times as compared with the traditional ceramic method. Final and milled products were Studied by X-ray powder diffraction at room and increasing temperatures, and by thermal analysis and scanning and high resolution transmission electron microscopy. (C) 2003 Elsevier Inc. All rights reserved.