The microstructure of ordered Ba(Mg1/3Ta2/3)O3

The microstructure of the ordered perovskite Ba(Mg1/3Ta2/3)O-3 was studied by means of direct imaging, using high-resolution electron microscopy, and by means of selected-area electron diffraction. 'Single' crystals are shown to be fragmented at different structural levels. The cubic BaO3 framework contains numerous twins and stacking faults. Single domains of this framework are further fragmented by the potential occurrence of four orientation variants and of three translation variants in each orientation variant of the superstructure. The observations are consistent with the assumption that, at a temperature close to the melting point, an order-disorder transition of the B-cation sublattice occurs within the already-formed BaO3 framework.