Utilizing non-stoichiometry in Nd₂Zr₂O₇pyrochlore: exploring superior ionic conductors

Abstract

The optimisation and control of ordered and disordered regions in non-stoichiometric Nd2−xZr2+xO7+x/2pyrochlore system lead to enhancement of ionic conductivity.

Fingerprint of local disorder in long range ordered isometric pyrochlores

“…The patterns possess the characteristic superstructure peaks of cubic pyrochlore, Fd-3m and the lattice parameters of 10.8019(1), 10.6911(1), 10.5753(1) and 10.5533(1) Å were obtained for respectively La 2 Zr 2 O 7 , Nd 2 Zr 2 O 7 , Sm 2 Zr 2 O 7 and Eu 2 Zr 2 O 7 . These values are in general agreement with the one previously published 26,34,36–44 and, especially with stoichiometric pyrochlores. As expected, there is an increase of the lattice parameter as a function of the ionic radii (Supplementary Figure 2).…”

“…We therefore focus our discussion on modes A*, E*, F*, G* and H* which differ between ordered and disordered pyrochlore spectra. As mode A* appears in the spectrum of Sm 2 Zr 2 O 7 and Eu 2 Zr 2 O 7 (its absence is also confirmed in their equivalent 16 O Raman spectra reported in literature 28,43,44 ) it is unlikely that neither involves (O1, 8b) nor (O2, 48f) oxygens, since both sites are fully occupied in the ideal pyrochlore. To better understand the mode A*, we have to pursue our discussion of the other Raman bands.…”

“…Alarmingly, many discrepancies exist in published assignments thereof  56–58 . The most common method to interpret the Raman data relies on the spectral comparison with each other and between different pyrochlore families 42–44 . Here, we take an alternative approach and attribute the different modes by comparing the spectra through this Ln 2 Zr 2 O 7 series.…”

Electrode and Electrolyte Materials From Atomistic Simulations: Properties of LixFEPO4 Electrode and Zircon-Based Ionic Conductors

“…Zirconium-based ceramics have been shown to posses interesting ion-conduction characteristics (Diazguillen et al, 2008;Mandal et al, 2008;Xia et al, 2010;Anithakumari et al, 2016;Li and Kowalski, 2018), with yttria stabilized zirconia being one of the fastest ionic conductors (Kilo et al, 2003;Krishnamurthy et al, 2005b). It is thus used as solid electrolyte in various energy storage devices (Zakaria et al, 2020).…”

“…It is thus used as solid electrolyte in various energy storage devices (Zakaria et al, 2020). The fast oxygen conduction properties are associated with formation and distribution of vacant sites (in fluorite and pyrochlore, Bukaemskiy et al, 2021) and interesting short-and long-range ordering phenomena (Wuensch, 2000;Yamamura, 2003;Anithakumari et al, 2016;Drey et al, 2020;Kowalski, 2020;Bukaemskiy et al, 2021). For instance, certain pyrochlore compounds exhibit high ionic conductivity (e.g., Eu 2 Zr 2 O 7 , Yamamura, 2003) and form a stable, cation-disordered solid phase (defect fluorite, Li et al, 2015).…”