Two types of domain boundaries in lanthanum magnesium niobate

Microstructural studies of the domain boundaries in the complex perovskite compound lanthanum magnesium niobate (La[Mg2/3Nb1/3]O-3, LMN) were conducte d using transmission electron microscopy. Both the 1:1 chemical ordering of B-site cations and the tilting of oxygen octahedra affected the domain bou ndaries. Two types of domain boundaries were observed. In addition to the p resence of antiphase boundaries, which were insensitive to the crystallogra phic planes, ferroelastic domain boundaries that were caused by the phase t ransition due to the tilting of oxygen octahedra also were present. In some grains, only one type of oxygen tilting was present, which resulted in a s ingle domain in one grain. Two or three domains were observed in a grain wh ere the walls were parallel to the {110} plane. Many domains also were obse rved in a grain that had boundaries whose linear characteristics were gradu ally reduced.