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Positive and negative monoclinic deformation of corundum‐type trigonal crystal structures of M 2 O 3 metal oxides
Author(s) -
Fabrykiewicz Piotr,
Przeniosło Radosław,
Sosnowska Izabela,
Fauth François
Publication year - 2018
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520618014968
Subject(s) - corundum , crystallography , monoclinic crystal system , metal , materials science , transition metal , crystal structure , type (biology) , distortion (music) , deformation (meteorology) , chemistry , metallurgy , geology , composite material , paleontology , amplifier , biochemistry , optoelectronics , cmos , catalysis
The crystal structures of several transition metal oxides, Ti 2 O 3 , V 2 O 3 , Cr 2 O 3 , Al 2 O 3 and α‐Fe 2 O 3 , are studied using synchrotron radiation X‐ray powder diffraction. The observed angular dependence of the integral breadths is described by two models: (i) the distorted corundum‐type structure model described by the space group C 2/ c and (ii) the Stephens model of anisotropic Bragg peak broadening. These two models are shown to be equivalent. Ti 2 O 3 , V 2 O 3 and Cr 2 O 3 show a `positive' distortion which is related to the possible metal–metal bond suggested by Goodenough in the literature (the deformation leads to shorter metal–metal distances) whereas Al 2 O 3 and α‐Fe 2 O 3 show a `negative' distortion which leads to relatively longer metal–metal distances.