Mechanochemical synthesis of LaCrO₃ by grinding constituent oxides

Hydrous amorphous chromium oxide (Cr₂O₃·nH₂O) and crystalline one (Cr₂O₃) powders prepared by heating Cr(OH)₃·nH₂O at different temperatures were separately ground with La₂O₃ powder using a planetary ball mill at room temperature to investigate mechanochemical synthesis of LaCrO₃. Hydrous amorphous chromium oxide prepared reacts with La₂O₃ to form LaCrO₃ and the reaction proceeds with an increase in grinding time. No reaction takes place in the case of crystalline Cr₂O₃. The ground sample consists of agglomerates and large particles with size up to around 100 μm and shows low specific surface area of about 5 m²/g. The mechanochemical method can be also used to synthesize other chromium rare earth complex oxides by grinding the mixture of hydrous chromium oxide and rare earth (Pr, Nd and Sm) oxides.