Issue 8, 1976

A structrual theory for non-stoicheiometry. Part III. Defect fluorite-type structures: vacancy superstructures in ordered praseodymium oxides

Abstract

The hypostoicheiometric composition region MO2 –δ(0.286 [gt-or-equal]δ[gt-or-equal] 0) if binary lanthanoid oxides is re-examined in the light of new electron difraction data on ordered praseodymium oxides PrnO2n– 2 with n= 7,9,10,11, and 12. Model structures have been devised which are consistent with the topological requirements of the co-ordination defect (c.d.) and the implications of the new unit-cell data. The metal-centered pairing of c.d.s along [111]F, to yield the structural unit of composition Pr7O122, is a fundamental determinant in all phases. The vacancy sets for the triclinic homologues have been defined uniquely and those possible for the monoclinic phase β-Pr12O22 have been reduced to two alternatives. Planar ordering of anion vacancies characterizes both the triclinic (odd-n) and monoclinic (even-n) hormologues. Possible inter-relatios between their structures are analysed in terms of an extension of the crystallographic shear formalism.

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1976, 676-685

A structrual theory for non-stoicheiometry. Part III. Defect fluorite-type structures: vacancy superstructures in ordered praseodymium oxides

B. F. Hoskins and R. L. Martin, J. Chem. Soc., Dalton Trans., 1976, 676 DOI: 10.1039/DT9760000676

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