Ein neuer Perowskit mit Lücken im Anionenteil: Ba4[Na2W2O11]

A New Perowskite with Deficiencies in the Oxygen Part: Ba₄Na₂W₂O₁₁] For the first time colourless single crystals of Ba₂NaWO_5.5 were prepared by reaction of Na₄WO₅ 2] and ?BaO₂”? Ba:Na:W = 4:4:1, Ni-cylinder, 725°C, 35 d]. Single crystal data 432 of 505 I₀ (hkl), Four-circle-diffractometer Siemens AED2, MoKα , R = 6.1%, R_w = 5,6%] verify the space group P mmm with a = 579.16(8), b = 580.85(8), c = 859.4(1) pm, Z = 1. The structure is based upon the CaTiO₃-type of structure. Ba²⁺ take the place of Ca²⁺ meanwhile Ti⁴⁺ is substituted alternately by W⁶⁺ and Na⁺. Complete occupation of all lattice positions would lead to a deficite of positive charge. This is compensate by deficiencies in the oxygen part of the lattice. Related to Na(1)₁Na(2)₁W(1)₁W(2)₁O(1)₄O(2)₂O(3)₂O(4)₃] these deficiencies are statistically distributed on O(4). Structural relations are deduced by Schlegel-Diagrams. The Madelung Part of Lattice Energie, MAPLE, Effektive Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.