The structure and properties of misfit layer compounds

Abstract

The purpose of this article is to provide an introduction to the class of compounds known as misfit layer compounds.An example of a misfit layer compound is (NdS)1.2NbS2 In the present study this material was made by heating appropriate amounts of sulphur powder, niobium powder and neodymium chips in an evacuated quartz tube at 850°C for 12 hours. A subsequent five day process involving transport and back transport at 1000°C in the presence of iodine as transport agent led to the formation of lustrous crystal platelets suitable for electron microscopy and electron diffraction studies. The orthorhombic material consists of alternate layers of NdS (two atoms thick) and layers of NbS2 (three atoms thick) each perpendicular to the c-axis. Fig. 1 shows a [100] view of the structure observed in recent studies. Though it differs from the structure reported in other work, both reported forms have features in common which are characteristic of all misfit layer compounds.