Synthesis of Perovskite Type-RERh3Bx (RE=La, Lu) Compounds and Study on Their Boron Nonstoichiometry and Hardness

Polycrystalline samples of LaRh3Bx and LuRh3Bx have been successfully synthesized by the arc melting method. Stoichiometric compositions of LaRh3B and LuRh3B have the perovskite-type cubic structure (space group Pm3m) and lattice parameter a=0.4251(1)nm and a=0.4126(1)nm, respectively. LaRh3B has no nonstoichiometry of boron. On the other hand, perovskite-type LuRh3Bx exists in the range of 0.3≤x≤1.000; the lattice parameter a of the perovskite-type cubic cell increases with increasing boron content x in the compound. The stoichiometric LaRh3B and LuRh3B have micro-Vickers hardness of 4.2 (±0.1) GPa and 7.7 (±0.5) GPa, respectively. The hardness of the LuRh3Bx increases with increasing the B content.