Disorder in Ho₂Ti_2−xZr_xO₇: pyrochlore to defect fluorite solid solution series

Abstract

Combined neutron and X-ray total scattering with calorimetric measurements of the solid solution series Ho2Ti2−xZrxO7 reveals a complex order–disorder transition across short, intermediate, and long length scales induced by chemical substitution.

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

“…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).…”

“…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). Such phases show interesting short-and long-range ordering (Shamblin et al, 2016;Drey et al, 2020;Kowalski, 2020;Bukaemskiy et al, 2021), with distribution of vacancies determining the amplitude of pre-exponential factor and efficiency of ionic conduction (Bukaemskiy et al, 2021). For instance, Bukaemskiy et al (2021) demonstrated that the maximum of ionic conductivity in YO 1.5 − ZrO 2 system occurs at x = 0.146 due to vacancy avoidance phenomenon and related vacancy jump probability.…”

A Comparison of Order-Disorder in Several Families of Cubic Oxides

“…The (A/B)O 7 layer in which partial disorder between A and B cations is marked with blue polyhedra for clarity in (B) . Figure has been drawn based on the crystallographic data from the literature ( Drey et al, 2020 ; Gussev et al, 2020 ). The crystal structures are drawn using the software VESTA ( Momma and Izumi, 2008 ).…”

“…AO 8 -BO 6 and AO 7 layers arrange alternately to form the overall structure ( Gussev et al, 2020 ). However, in A 2 3+ M 2 4+ O 7 , 8c sites are occupied equally by both A 3+ and B 4+ forming (A/B)O 7 polyhedral layer leading to disorder ( Shamblin et al, 2016a ; Drey et al, 2020 ). So, the structure can be seen as an alternating arrangement of ordered and disordered layers in weberite-type, A 2 M 2 O 7 .…”

“…Each simple structure (aristotype) is the parent of more complex structures showing ordering on anion and/or cation sublattices and the formation of layered structures. Modern diffraction and spectroscopy enable characterization of order on different length scales, with short-range order producing lower symmetry locally being detected increasingly often in nominally cubic structures ( Radhakrishnan et al, 2011 ; Shamblin et al, 2016a ; Shamblin et al, 2016b ; Martel et al, 2017 ; Shamblin et al, 2018 ; Moran et al, 2019 ; Drey et al, 2020 ). The details of ordering are different in each structural family.…”