Non-Condensed (Oxo)Nitridosilicates: La-3[SiN4]F and the Polymorph o-La-3[SiN3O]O

作者：Durach Dajana; Schnick Wolfgang^*

来源：European Journal of Inorganic Chemistry, 2015, 2015(24): 4095-4100.

DOI：10.1002/ejic.201500644

• Solid-state structures
• Nitrides
• Solid-state reactions
• Polymorphism
• Lanthanum

The isotypic compounds La-3[SiN4]F and La-3[SiN3O]O were synthesized in a radio-frequency furnace at 1600 degrees C. The crystal structures [Pnma (no. 62), Z = 4; La-3(SiN4)F: a = 9.970(3), b = 7.697(2), c = 6.897(2) angstrom, V = 529.3(3) angstrom(3); La-3(SiON3)O: a = 9.950(2), b = 7.6160(15), c = 6.9080(14) angstrom, V = 523.48(18) angstrom(3)] were elucidated from single-crystal X-ray diffraction data and corroborated by Rietveld refinement, lattice-energy calculations (Madelung part of lattice energy, MAPLE) and Raman/FTIR spectroscopy. Both compounds are homeotypic with Na2Pr[GeO4]OH forming a network of vertex-sharing FLa6/OLa6 octahedra, whose voids are filled with non-condensed SiN4/SiN3O tetrahedra. o-La-3[SiON3]O is the orthorhombic polymorph of this compound, which probably represents the high-temperasture modification, whereas the tetragonal polymorph t-La-3[SiON3]O represents the low-temperature modification. While the space group of the t-polymorph [I4/mcm (no. 140)] differs from the new La-3[SiN4]F and o-La-3[SiN3O]O, the crystal structure contains the same linking pattern.

• 出版日期2015-8