Anomalous behavior of hardness and crystal structure in CeRh3Bx (x = 0-1) phase

We have examined the relationship between hardness and crystal structure of a Cu3Au-type compound CeRh3Bx (x = 0-1) by electron diffraction and high-resolution electron microscopy. The electron diffraction revealed 1/2 1/2 1/2-type superlattice reflections and fine satellite ones in B content range of 0.4 < x < 0.5, where anomalous decrease of hardness was observed. The observed high-resolution image taken with a diffraction pattern showing the satellite reflections along the [0 1 1] direction shows a domain structure with size of about 3 nm, and a lattice modulation and some edge dislocations have been observed at boundaries between the domains. Conclusively, ordering of B atoms and followed by the appearance of the long-ranged modulated structure could lead to the anomalous behavior of hardness in CeRh3Bx.