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 image (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 image. 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.