Relationship between boron content and hardness and oxidation resistance of the nonstoichiometric perovskite type-ScRh3Bx compound

Polycrystalline samples of ScRh3Bx, which consists of reactive Se and high melting point Rh and B elements, have been successfully synthesized by the arc melting method. ScRh3Bx has the perovskite cubic structure (space group Pm3m), Perovskite-type 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 has the AuCu3 type structure (space group Pm3m). The lattice parameter a in annealed ScRh3Bx depends on x, and varies linearly from a = 0,3903 (1) nm (x = 0) to 0.40799 (3) nm (x = 1.000). The micro-Vickers hardness of the annealed ScRh3Bx inc reases with increasing B content in the range x = 0-1.000, from 1.9 (+/-0.1 ) GPa for ScRh3 (0 mol%B) to 9.9 (+/-0.1)GPa for ScRh3B1.000 (20 mol%B), TG analysis indicates that the onset temperature of oxidation for ScRh3B1.000 is 595 degrees C, The sharp exothermic peak of the DTA curve is found at 7 97 degrees C. Weight gain of the sample by heating in air up to 1200 degree s C is 12.7%. The sample changed to Rh plus Sc2O3 and ScBO3 after oxidation , The weight gain of the sample decreases with decreasing boron content.