Structural characterizations of 6H-barium niobium sulfide

The structural characteristics of BaNb5.67S10.8 were studied using high res olution transmission electron microscopy (HRTEM). The BaNb5.67S10.8 crystal s are composed of overlapped parallel Rakes lying in the (001) plane of the hexagonal system. The misorientations displayed in the selected area elect ron diffraction (SAED) patterns indicated the presence of rotational stacki ng faults around the c-axis. The HRTEM image showed that cleavage appeared preferentially between a Ba-S layer and the successive S layer. The occurre nce of the structural imperfections was found to relate to the weak bonding between Ba and Nb on the one hand, and Nb and S on the other hand in the o ctahedron. The formation of a 3a x 3a two-dimensional superlattice was obse rved by electron diffraction. This was suggested to be due to atom ordering in the Ba-S hexagonal net. (C) 1998 Acta Metallurgica Inc. Published by El sevier Science Ltd. All rights reserved.