Lamellar structures in neodymium borides

Samples with the nominal composition Nd2B5 contain strongly disordered crystals composed of nanosized (100) lamellae. Most commonly, a polysynthetic twinning based on a fourfold rotation separates the lamellae at coherent boundaries. The structure of the twin interface contains a pseudo fourfold arrangement of B atoms as derived from electron microscopy techniques. Such pseudo-symmetry serves for a rationalization of the twinning. Additionally, a chemical intergrowth of Nd2B5 and NdB4 lamellae based on related structural building units can be observed. Further HRTEM examinations allow the identification of a new structural variant of neodymium borides.