Preparation, crystal structure and physical properties of ternary compounds (R3N)In, R = rare-earth metal

The compounds (R3N)In (R = Sc, La-Nd, Sm, Gd-Tm, Lu) were synthesized by arc melting and sintering reactions from the binaries RN and R2In. Combined Rietveld refinements on X-ray and neutron powder diffraction data on the Ce-phase and X-ray diffraction for the other phases reveal the compounds (R3N)In to crystallize in the perovskite structure ((Ce3N)In: Pm (3) over barm, a = 504.89(2) pm; Rietveld: neutron powder diffraction: R-F = 0.056, R-Bragg = 0.104, X-ray powder diffraction: R-F = 0.069, R-Bragg = 0.115; refined composition Ce3InN0.92(1), chemical analysis Ce3InN0.91(2)O0.05(1)). Compounds R3In (AuCu3 structure type) are known for R = La-Sm. Nitrogen is able to stabilize this AuCu3-substructure with R = Gd-Tm, Lu and Sc. In measurements of the magnetic susceptibility (Ce, Pr, Nd, Sm, Tb: antiferromagnetic ordering at low temperature) and X-ray absorption spectroscopy at the R-L-III-edges the rare-earth atoms behave like R3+ species in insulating compounds. The electrical resistivity of the Sc, Ce and Nd compounds shows metallic temperature dependence. Chemical bonding was analyzed via LDA-COHP calculations for (La3N)In showing ionic polyhedra NLa6/2 embedded in a metallic matrix. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.