Solid solution range of boron, microhardness and oxidation resistance of the perovskite type RERh3Bx (RE=Gd, Y, Sc) compounds

Polycrystalline samples of RERh3Bx (RE=Gd, Y, Sc), which consists of a reactive RE and high melting point Rh and B elements, are successfully synthesized by the are melting method. RERh3Bx compounds have the perovskite type cubic structure (space group Pn3m). Perovskite type phases of GdRh3Bx and YRh3Bx exist in the range of similar to 0.444 less than or equal to x less than or equal to 1.000. On the other hand, phase of ScRh3Bx exists in the range of 0 less than or equal to x less than or equal to 1.000 (0 to 20 mol% B). ScRh3, in the case of x=0, has AuCu3 type structure; its space group is also Pm3m. The lattice parameter a in RERh(3)Bx depends on x and the Value of a increases with increasing boron content x. The value of Vickers microhardness of the RERh3Bx at room temperature ranges from 6 to 10 Cpa. According to thermo-gravimetric and differential thermal analysis for RERh3Bx (RE=Gd, Y) heating up to 1200 degrees C in air, a mixed phase of REBO3 and Rh is identified as II oxidized product. In the case of ScRh3B, the oxidized product consists of Rh, Sc2O3 and ScBO3. (C) 1999 Elsevier Science S.A. All rights reserved.