Five Co-ordinated Titanium in K2Ti2O5


IT is widely believed that oxygen atoms may be extracted at random from the lattices of metallic oxides, and X-ray powder photographs have suggested that little or no modification of the structure of the original stoichiometric substance occurs. In particular, evidence has been adduced that the perovskite lattice can persist between the limits ABO 3ABO 2.5, provided that the six co-ordinated ion B is one of the metals, titanium, vanadium, cobalt or iron1. In order to evaluate this proposal, we are examining the crystal structures of ordered, oxygen-deficient compounds in which the ionic radii comply with the rules enunciated by Goldschmidt2 for the perovskite structure. K2Ti2O5 was recently reported by Schmitz-Dumont and Reckhard3 to have a large unit cell of low symmetry, and this could, perhaps, be due to the regular omission of some of the oxygens from a perovskite lattice. We now wish to report briefly that a complete X-ray structure determination does not support this view.

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    Goldschmidt, V. M., Barth, T., and Lunge, G., Skr. norske Vidensk. Akad., Matem.–Naturvid. Kl., No. 7 (1925).

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    Schmitz-Dumont, O., and Reckhard, H., Monatsh. Chemie, 90, 134 (1959).

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ANDERSSON, S., WADSLEY, A. Five Co-ordinated Titanium in K2Ti2O5 . Nature 187, 499–500 (1960).

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