The synthesis and structural characterization of the new ternary nitrides: Ca4TiN4 and Ca5NbN5

The ternary nitrides, Ca4TiN4 and Ca5NbN5, were synthesized in sealed niobium tubes using lithium nitride as a flux at 900 and 1050 °C, respectively. The structures of both compounds were solved from single-crystal X-ray diffraction data. Ca4TiN4 is the first example of a calcium group IV nitride; it crystallizes in the triclinic space group P1¯ (No. 2) with cell parameters a=5.9757(5) Å, b=6.0129(5) Å, c=6.0116(12) Å, α=71.565(4)°, β=79.471(4)°, γ  =68.258(4)° and Z=2Z=2. Ca4TiN4 is isostructural with Na4TiO4 and contains tetrahedral TiN4 units connected through edges and corners to CaN4 tetrahedra and CaN5 square pyramids. Ca5NbN5 crystallizes in the monoclinic space group C2/m (No. 12) with cell parameters a=11.922(7) Å, b=6.878(5) Å, c=8.936(7) Å, β=101.22(3)° and Z=4. Ca5NbN5 is isostructural with Ba5NbN5; the structure contains NbN4 tetrahedra that share vertices with CaN5 trigonal bipyramids.

Ca4TiN4: titanium tetrahedron (center) corner-sharing with calcium polyhedra.Figure optionsDownload as PowerPoint slide