Microstructural changes in lanthanum-doped barium magnesium niobate

Observations of microstructural changes in (Ba0.95La0.05)(Mg0.35Nb0.65)O-3 and (Ba0.925La0.075)(Mg0.36Nb0.64)O-3 (BLMN) were carried out using high-re solution transmission electronmicroscopy (HRTEM) and synchrotron powder X-r ay diffractometry (XRD). In both samples, not only 1:1 and 1:2 ordered doma ins coexisted in a single grain, but also the intermediate phase, whose str ucture had a superlattice:modulation of 1.42 nm, which was equivalent to 6 times the unit:cube of disordered perovskite found on the nanoscale, The or dered 1:2 domains gradually transformed to 1:1 ordered structure through th e formation of an intermediate superlattice structure that comprised 6 x 6 x 6 cubic-unit cells with different chemical orderings of B-site ions in B- site lattices, Also, the features of thin plates could be detected by XRD p atterns and HRTEM, When the thicknesses were,very thin, about several atomi c distances, stacking faults occurred on (111) planes. However, when their thicknesses were >50 nm, the thin plates existed as a transition phase with their own structure. They were coherent with the matrix and continuously d ecomposed into the matrix phase by the lateral migration of the interfaces.