Synthesis and Structure of Oxygen Deficient Lead-Technetium Pyrochlore, the First Example of a Valence V Technetium Oxide

The structure of lead-technetium pyrochlore has been refined in space group Fd (3) over barm with a = 10.36584(2) angstrom using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O7-d. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi2Tc2O7-d. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide.

Automated summary

The lead-technetium pyrochlore structure has been refined using synchrotron X-ray and neutron powder diffraction data, with electron diffraction confirming the results. The oxygen deficient oxide has a stoichiometry of Pb2Tc2O7-d. X-ray absorption spectroscopy at the Tc K-edge showed that the valence of Tc is greater than 4.0, while Raman spectroscopy confirmed the presence of disorder, indicating that this pyrochlore is the first example of a valence V technetium oxide.