Hardness and Oxidation Resistance of Nonstoichiometric ErRh₃B_x-Perovskite

Abstract

Polycrystals of ErRh₃B_x are synthesized by arc melting. The compounds of ErRh₃B_x have a perovskite-type cubic structure (space groups Pm3m). The nonstoichiometric phase exists for the boron content from x=1.000 (20mol% B) to 0.61 (13.3mol% B). The lattice parameter of a depends on x, and varies linearly from a=0.4151nm (x=1.000) to 0.4063nm (x=0.61). The micro-Vickers hardness of the ErRh₃B_x compaunds increases with increasing their B content. The hardness of ErRh₃B_1.000 (20mol% B) sample is 8.6±0.3GPa. The thermo gravimetric curve indicates that the onset-temperature of oxidation for ErRh₃B_1.000 is 1303K. The weight gain of ErRh₃B_1.000 during heating in air to 1473K is 0.7%.