Ln₃[SiON₃]O (Ln = La, Ce, Pr) - three oxonitridosilicate oxides with crystal structures derived from the anti-perovskite structure type

The oxonitridosilicate oxides Ln₃[SiON₃]O with Ln = La, Ce, Pr were obtained by high-temperature syntheses (1450-1600 C) in a radio-frequency furnace. The crystal structures were determined from single-crystal X-ray diffraction data and confirmed by Rietveld refinements. The compounds Ln₃[SiON₃]O crystallize in space group I4/mcm (La₃[SiON₃]O: a = 6.8224(10), c = 11.074(2) Aa, Z = 4; R₁ = 0.0240; Ce₃[SiON₃]O: a = 6.7233(10), c = 11.069(2) Aa, Z = 4, R₁ = 0.0234; Pr₃[SiON₃]O: a = 6.6979(9), c = 11.005(2) Aa, Z = 4; R₁ = 0.0156) and they were found to be isotypic with Gd₃[SiON₃]O, whose structure derives from the anti-perovskite structure type. In the crystal structure there are elongated OLn₆-octahedra, which are interconnected through common vertices. In the cavities of this network there are exclusively non-condensed SiON₃ tetrahedra. ²⁹Si solid-state NMR investigations, lattice energy calculations (MAPLE) and EDX measurements confirmed the crystal structure and the chemical compositions. For Ce₃[SiON₃]O, magnetic susceptibility measurements were carried out and the paramagnetic behavior with an experimental magnetic moment of 2.2 μ_B per cerium atom indicates Ce³⁺. (Abstract Copyright [2010], Wiley Periodicals, Inc.)