Abstract
Hollandite-type tunnel structures of K 1.50Al 1.50Ti 6.50O 16 and Rb 1.47Al 1.47Ti 6.53O 16 were refined; final R- and wR-factors were 2.24 3.30 and 2.98 3.32% , respectively. The structures were compared with those of K 1.54Mg 0.77Ti 7.23O 16 and BaAl 2Ti 6O 16 from the viewpoint of crystal chemistry. The substitutions of K by Rb and Ba make an anisotropic deformation on the frameworks relative to that of K 1.50Al 1.50Ti 6.50O 16, whereas the replacement of Al by Mg changes more uniformly the network by enlarging octahedra themselves. The octahedron in the three priderites, (Rb, K, or Ba) x Al y Ti 8− y O 16, becomes larger and gets more regular in that order, but the off-center displacement of the octahedral cation also becomes larger. The volume-dependent octahedron regularity is due to the sensitive movement of bottleneck oxygen atoms with the differences in charge and/or size among the tunnel ions. The volume dependency of the off-centering seems to be explicable on the basis of Megaw's theory.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
