Preparation and Partial Characterization of Two New Hexavalent Uranium Metal Uranates

Abstract

The preparation, chemical characterization and structural investigation by X-ray and electron diffraction of two uranates (VI), namely Sr₅U₃O₁₄ and of Pb₁₁U₅O₂₆, are reported. The strontium compound, the unit cell of which is metrically tetragonal with a = 11.248(5), c = 11.086(5) Ǻ, Z = 4, was shown by electron diffraction to be orthorhombic, space group Pbca with a = b. Crystals of Sr₅U₃O₁₄ are invariably submicroscopically twinned and, because of the identity of a and b, mimic tetragonal symmetry. The lead uranate , Pb₁₁U₅O₂₆, was shown to be a long-period superstructure with unit cell dimensions a = 44.54, b = 15.586, c = 8.241 Ǻ, Z = 8.