AUTHOR=Kennedy Brendan J. , Ablott Timothy A. , Avdeev Maxim , Carter Melody L. , Losurdo Linda , Saura-Muzquiz Matilde , Thorogood Kevin J. , Ting Jimmy , Wallwork Kia S. , Zhang Zhaoming , Zhu Hanliang , Thorogood Gordon J. 

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

JOURNAL=Frontiers in Chemistry

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.706269

DOI=10.3389/fchem.2021.706269

ISSN=2296-2646

ABSTRACT=<p>The structure of lead-technetium pyrochlore has been refined in space group <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>F</mml:mi><mml:mi>d</mml:mi><mml:mrow><mml:mover accent="true"><mml:mn>3</mml:mn><mml:mo>¯</mml:mo></mml:mover></mml:mrow><mml:mi>m</mml:mi></mml:mrow></mml:math></inline-formula> with <italic>a</italic> = 10.36584(2) Å 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 Pb<sub>2</sub>Tc<sub>2</sub>O<sub>7-d</sub>. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi<sub>2</sub>Tc<sub>2</sub>O<sub>7-d</sub>. 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.</p>