Synthesis of Li2MO3 (M = Ti or Zr) by the combustion method

The advantages and disadvantages of the combustion method to prepare Li2TiO3 and Li2ZrO3 ceramics were studied. Firstly, the ceramic powders were prepared by the combustion process using LiOH, MO2 (where M = Ti or Zr) and urea in different molar ratios (from 2:1:3 to 3:1:3) at different temperatures for 5 minutes. Li2TiO3 and Li2ZrO3 were also obtained by the solid-state method, and the results were compared with those obtained by the combustion process. The powders were characterized by X-ray diffraction and scanning electron microscopy. It was found that the combustion process reduces the synthesis time of Li2TiO3 (1 minute at 750 degrees C), but it does not have any advantage on producing Li2ZrO3, due to thermodynamic factors. On the other hand, the combustion process produces carbon contaminants in the solids. It was necessary to add excess of lithium hydroxide, in order to compensate the quantity of Li sublimated during the production of the ceramics. Finally, it seems that both reactions follow the same mechanism, which is determined by the lithium diffusion into the metal oxides. (C) 2006 Elsevier SAS. All rights reserved