Ternary Intermetallic Compounds LnMn2Al10 (Ln = Y, La-Nd, Sm, Gd-Dy) and LnRe2Al10 (Ln = Ce, Pr, Sm) with CaCr2Al10-Type Structure

Abstract

Abstract The twelve title compounds have been prepared for the first time. Their CaCr2Al10-type structure (P4/nmm, Z = 4) was refined from single-crystal X-ray data for the three representatives TbMnAl10 (a = 1274.3(2) pm, c = 511.4(2) pm, R = 0.025 for 680 structure factors F and 43 variable parameters V), CeRe2Al10 (a = 1295.5(5) pm, c = 517.2(4) pm, R = 0.054 for 810 F and 46 V), and SmRe2Al10 (a = 1291.5(2) pm, c = 516.5(1) pm, R = 0.021 for 622 F and 46 V). The atomic positions of the lanthanoid and transition metal atoms are fully occupied. Significant deviations from the full occupancies were observed for two aluminum sites in TbMn2Al10 and for all five aluminum sites of the two rhenium-containing compounds, resulting in the compositions TbMn2Al9.63(2), CeRe2Al9.52(8), and SmRe2Al9.16(9). The cell volume of CeRe2Al10 and to a smaller extent also that of CeMn2Al10 indicate mixed or intermediate +III/+IV valencies of the cerium atoms in these compounds. The structural relationships between the three closely related body-centered tetragonal structures of ThMn12, CeMniAl8, DyFe6Al6 and the primitive tetragonal structure of CaCr2Al10 are briefly discussed.