(Sr3N)E and (Ba3N)E (E = Sb, Bi):: Synthesis, crystal structures, and physical properties

Single phase powders of (Sr3N)Sb, (Sr3N)Bi (Pm (3) over barm, No. 221, Z = 1, Sb: a = 517.25(2) pm, V = 138.390(8) . 10(6) pm(3), Bi: a = 520.691(8) pm, V = 141.170(4) . 106 pm(3)), (Ba3N)Sb, and (Ba3N)Bi (P6(3)/mmc, No. 194, Z = 2, Sb: a = 753.33(3) pm, c = 664.45(3) pm, V = 326.56(2) . 10(6) pm(3), Bi: a = 761.28(4) pm, c = 668.05(3) pm, V = 335.30(2) . 10(6) pm(3)) were obtained from reactions of melt beads of the respective elements with bulk compositions of A(3)E (A = Sr, Ba; E Sb, Bi) in nitrogen atmosphere of ambient pressure at T = 1070 K (Sr) and T = 1120 K (Ba). The compositions were derived from chemical analyses and supported by Rietveld refinements based on powder X-ray diffraction patterns. The Sr containing compounds crystallize in the cubic antiperovskite type arrangement, the Ba containing compounds in the hexagonal anti-BaNiO3 structure type. Magnetic susceptibility and electrical resistivity data indicate that the compounds are diamagnetic semiconductors. The optical band gaps of (Sr3N)Sb and (Sr3N)Bi were determined by diffuse reflectivity to 1.15 eV and 0.89 eV, respectively. The experimental results are in agreement with electronic structure calculations. Chemical bonding is characterized in a simplified picture as ionic with significant orbital mixing.