Abstract
The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques. The degree of antimony disproportionation in Sb3+ and Sb5+ valence states has been directly determined around 36% and 64%, respectively, using X-ray absorption near edge structure (XANES). These findings are in excellent agreement with our Rietveld analysis of synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) results. Moreover, the highly distorted Sb3+ coordination due to its lone electron pair has been critically revisited. The bonding distances and coordination of Sb3+ and Sb5+ species closely agree with an extensive dynamic and crystallographic determination using the Extended X-ray Absorption Fine Structure (EXAFS) technique. Most importantly, the specific local disorder of the two distinctive Sb ions has been crosschecked monitoring their unusual Debye–Waller factors.
Highlights
The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques
A Fourier difference density map performed from neutron powder diffraction (NPD) data, collected at room temperature (RT), led to negative scattering density at 8a position and a positive density dispersed in its vicinity, as shown in Supplementary Fig. S2
The complementary structural and dynamic study of Sb6O13 using long- and short-range diffraction techniques together with X-ray Absorption Fine Spectroscopy confirms that this particular Sb-oxide can be precisely described as a defect pyrochlore, defined in the Fd3m space group
Summary
The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques. The broad family of pyrochlore oxides, with the general formula A2B2O6O′(space group: Fd3m , Z = 8) displays an incomparable flexibility, concerning cationic substitutions, atomic vacancies, structural defects, and related superstructures, accounting for the wide panoply of physical properties and a pplications[8], including thermal, electrical, and magnetic properties. They have shown high resistance to radiation damage and temperature, and improved catalytic effects on water splitting[9,10,11,12]. The free space of the above (B2O6) framework can be filled with a second framework related to the (A2O′) units, or with separate individual ions and/or H 2O molecules
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