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On the Crystal Chemistry of Alkali‐, Alkaline‐Earth‐, Rare Earth‐Oxozirconates and Zirconium Oxides
Author(s) -
MüllerBuschbaum Hanskarl
Publication year - 2010
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201000037
Subject(s) - zirconium , coordination number , octahedron , crystallography , alkali metal , tetragonal crystal system , crystal chemistry , crystal structure , chemistry , inorganic chemistry , ion , materials science , organic chemistry
The contribution on oxozirconates gives a view on the crystal chemistry of zirconium compounds with large cations, like alkaline, alkaline‐earth and rare earth elements. This is completed by a short overview of the structure types of ZrO 2 synthesized by different methods, temperatures and pressures. The most important observation is the missing reflection of the coordination chemistry of zirconiumoxides into the oxozirconates. Usual coordination numbers of zirconium in zirconiumoxide are CN = 8 and occasionally CN = 9. The described oxozirconates instead show mainly octahedral (CN = 6) coordination (such as Li 2 ZrO 3 , K 2 Zr 2 O 5 , Li 0.8 K 0.9 (LiMgZr)Zr 2 O 6.5 , Li 6 Zr 2 O 9 , K 4 Zr 5 O 12 , K 2 Li 14 Zr 3 O 14 , Pb 0.5 Ca 0.5 ZrO 3 , Nd 2 Zr 2 O 7 , BaCe x Zr 1– x O 3 ). Exceptions with the coordination number six exhibit trigonal ZrO 6 ‐prisms (K 4 Zr 5 O 12 ). This facts result in the observation, that zirconium is a member of the anionic parts of the crystal structures. Lower coordination spheres are enforced by the cations. The larger a cation and the larger its amount in the chemical composition is, the lower the coordination number of zirconium gets. For example: CN Zr = 5 (tetragonal pyramid) in K 2 ZrO 3 , Cs 2 ZrO 3 ; CN Zr = 4 (tetrahedron) in Cs 4 ZrO 4 . Furthermore, Zr 4+ can also be found in statistical distribution with ions of the same size, like Li + and Mg 2+ . Calculations of the Madelung part of lattice energies of zirconium oxides show unexpected uniform data, independent from shape and size of the coordination polyhedra.