Phase evolution induced by mechanical milling in Ln2O3:TiO2 mixtures (Ln=Gd and Dy)

This paper presents a study of the phase evolution induced by mechanical milling in mixtures Ln2O3:TiO2 (Ln=Gd, Dy) with two different stoichiometries, 1:1 and 1:2. Starting from oxides, pyrochlores Ln2Ti2O7 and the hexagonal β-Ln2TiO5 forms were obtained at room temperature by milling the initial mixtures in a planetary ball mill using zirconia balls and mortars. Mechanically activated chemical reactions involve titanium oxide and the monoclinic B-Ln2O3, obtained this one during the initial stages of the milling process, from the starting highly symmetric cubic form, C-Ln2O3. Differential thermal analysis of the just milled powders showed in every case, the presence of an exothermic event at temperatures close to 800 °C which is thought to be due to some order-disorder event.