High-resolution electron microscopy study of hafnium nitride chloride

In this paper, it is shown the first high-resolution electron microscopy st udy of beta-HfNCl, the compound that upon lithium intercalation gives rise to a superconductor with a record critical temperature (25 K) for inorganic non-oxide materials. The results of this study performed on different batc hes confirm the structural model reported in previous papers and indicate t hat the intercalation capacity of the hafnium compound is strongly hindered by the presence of oxygen impurities in the sample. Independently, the gri nding of the samples is shown to induce displacement of the layers along th e c direction, thus preventing the diffusion of lithium into the van der Wa als gap and hence the induction of superconductivity.