Dependency of mechanochemical reactions forming complex oxides on the crystal structures of starting oxides

摘要

Mechanochemical reactions applicable to syntheses of perovskite-type compounds, LaMO3, where M is trivalent metals, are taken as examples to investigate effects of crystal structures of starting materials, M 2O3, on the reactions. The investigated oxides M 2O3 are categorized into two groups: one is the corundum structure and the other the non-corundum structure. Under the experimental conditions, it has been found that the oxides with non-corundum structure react easily with La2O3 by their co-grinding at room temperature to form the corresponding compounds. On the contrary, none of such reactions can be occurred for the oxides with corundum structure. The difference has been discussed based on the grinding-induced phase transformation from loose packing of atoms to close packing of atoms. Based on the results, the extension to the synthesis of other compounds such as CrO2 is presented.