Zwei neue Verbindungen mit Zink in tetragonal pyramidaler Koordination: BaZnDy2O5 und Ba1,25ZnHo2O5,25 (Ba5Zn4Ho8O21)

New Compounds with Zinc in Square Pyramidal Coordination: BaZnDy₂O₅ and Ba_1.25ZnHo₂O_5.25 (Ba₅Zn₄Ho₈O₂₁). Single crystals of (I): BaZnDy₂O₅ and (II): Ba₅Zn₄Ho₈O₂₁ were prepared by high temperature reactions and investigated by X-ray technique. (I) belongs to the BaCuLn₂O₅ type, space group D-Pbnm; a = 7.084; b = 12.368; c = 5.728 Å, Z = 4. (II) is isotypic to Ba₅Mn₄Ln₈O₂₁, space group C-I4/m; a = 13.779; c = 5.707 Å, Z = 2. The two different structure types are caused by the small difference in the composition of 0.25 BaO. Analogies and differences will be discussed. In addition the lattice constants of powder samples of Ba₅Zn₄Ln₈O₂₁ (Ln = Eu, Gd, Dy, Ho, Er and Y) are given.