Mechanosynthesis of nanocrystalline CaTi1-xMnxO3-δ

The mechanosynthesis of nanocrystalline CaTi1-xMnxO3-delta is reported for the first time. Powdered CaO, TiO2 anatase and Mn2O3 (Aldrich) were weighed in the appropriate stoichiometric quantities in order to obtain CaTi1-xMnxO3-delta (x=0.05, 0.10, 0.15, 0.20, 0.30, 030 and 0.80) and dry milled in a planetary high-energy ball mill, using zirconia containers and balls, with a 10:1 ball/mass ratio. The planetary rotation was kept constant at 650 rpm and the container at 1300 rpm, in the opposite direction. Powder XRD patterns revealed a perovskite forming from the early milling stages and a completed reaction after 180 min, with no apparent crystalline or amorphous intermediates, indicating significant Mn solubility in CaTiO3. Patterns show a decrease in lattice volume upon Mn substitution, as expected from the lower Mn3+ or Mn4+ ionic radii when compared to Ti4-. The average crystallite size is in the range 5-30 nm, as determined from Williamson-Hall plots and confirmed by high resolution transmission electron microscopy.