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Structural Principles for Anion‐Deficient, Fluorite‐Related Superstructures in the Zirconia‐Scandia System
Author(s) -
Bevan D. J. M.,
Mohyla J.,
Wallwork Kia S.,
Rossell H. J.,
Schweda Eberhard
Publication year - 2002
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 - 10.1002/1521-3749(200206)628:5<1180::aid-zaac1180>3.0.co;2-7
Subject(s) - crystallography , octahedron , tetrahedron , chemistry , crystal structure , stereochemistry
The concept of the coordination defect (CD) was used recently by Bevan and Martin [6] to describe the fluorite‐related superstructures of the intermediate Pr/Tb oxides. The CD is an octahedron of corner‐shared OM 4/8 tetrahedra enclosing a □M 4/8 tetrahedron, where □ represents an oxygen vacancy. Various linkages of CDs can define a polyhedral prism with contents appropriate to the phase composition, and this is designated the “ structural motif ”. The identical, parallel top and bottom planes of this prism are the “ motif plane ”. This concept is now extended to explore the structures of the ordered phases, delta , gamma and beta , which occur in the zirconia‐scandia system, the respective formulae being Zr 3 Sc 4 O 12 , Zr 10 Sc 4 O 26 and Zr 48 Sc 14 O 117 to Zr 50 Sc 12 O 118 . It is shown that the motif plane is the same in each of the known structures ( delta and gamma ), thus defining the close relationship between them. Possible models for the as‐yet unknown structure of the beta phase, in which this same motif plane occurs, can then be proposed.