Structural investigation of the ternary RM3B2 compounds

The crystal structure of the ternary borides CeRh3B2, CeCo3B2 structure type, P6/mmm space group, a = 5.470(2) Angstrom, c = 3.080(2) Angstrom, Z = 1, V = 79.81(2) Angstrom(3), rho = 9.789 g cm(-3), mu = 28.92 mm(-1) and YIr3B2, ErIr3B2 structure type, C2/m space group, a = 5.432(2) Angstrom, b = 9.398(4) Angstrom, c = 3.099(1) Angstrom, beta = 90.38(1)degrees, Z = 2, V = 158.2(1) Angstrom(3), rho = 14.425 g cm(-3), mu = 143.632 mm(-1) were refined to R = 0.0224, wR(2) = 0.0573 and R = 0.0467, wR(2) = 0.1138, respectively, from single crystal X-ray diffraction data of the "as cast" samples. The CeCO3B2 stucture type was confirmed for the CeRh3B2 compound, a = 5.47509(16)Angstrom, c = 3.08143(9) Angstrom from Rietveld refinement of X-ray powder diffraction data of the sample anealed at 1070 K (R-P = 2.76%, R-WP = 4.32%, R-B = 4.91%, R-F = 4.94%). The crystal structures of the annealed at 1070 K RIr3B2 (R = Ce, Nd and Y) and YRh3B2 compounds are more complicated. Different splittings of the reflexions in the X-ray powder patterns of these compounds can be an indication of different structure models related with the CeCo3B2, and ErIr3B2 structure types.