The microstructure of the ordered perovskite, Ba(Mg1/3Ta2/3)O3, was studied by means of direct imaging using high-resolution electron microscopy, and selected-area electron diffraction. The so-called single crystals were shown to be fragmented at several structural levels. The cubic BaO3 framework contained numerous twins and stacking faults. Single domains of this framework were further fragmented by the possible occurrence of 4 orientation variants and of 3 translation variants in each orientation variant of the superstructure. The observations were consistent with the assumption that, at temperatures close to the melting point, an order-disorder transition of the B-cation sub-lattice occurred within the already-formed BaO3 framework.

The Microstructure of Ordered Ba(Mg1/3Ta2/3)O3. C.H.Lei, G.Van Tendeloo, S.Amelinckx: Philosophical Magazine A, 2002, 82[2], 349-67