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The technetium perovskite CaTcO3 has been synthesized. Combining synchrotron X-ray and neutron diffraction, we found that CaTcO3 is an antiferromagnetic with a surprisingly high Neel temperature of ∼800 K. The transition to the magnetic state does not involve a structural change, but there is obvious magnetostriction. Electronic structure calculations confirm the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The structures of the defect pyrochlores AAl0.33W1.67O6 where A=K, Rb or Cs have been investigated using X-ray and neutron powder diffraction methods as well as the ab initio modelling program VASP. The three cubic pyrochlores exhibit a non-linear increase in lattice parameter with respect to ionic radius of the A cation as a consequence of displacive disorder of the A-type cations. Solid state 27Al MAS NMR studies of this pyrochlore system reveal shifts in the δ∼21–22ppm range that are indicative of pseudo-5 coordinate Al environments and emanate from distorted Al octahedral with one abnormally long Al–O bond. Solid state 39K, 85Rb, 87Rb and 133Cs MAS and static NMR studies reflect the local cation disorder demonstrated in the structural studies. [Copyright &y& Elsevier]

The structure of TcCo2O4has been determined using a combination of synchrotron X-ray and neutron powder diffraction methods. It has an inverse spinel structure where the Tc occupies the octahedral sites. Both the refined Tc–O distance and X-ray absorption spectra suggest the Tc is predominantly trivalent. [ABSTRACT FROM AUTHOR]