Stability of doped zirconia under extreme conditions: Toward long‐term and secure storage of radioactive waste

Abstract

Extreme temperatures and pressures were applied to systems based on stabilized zirconia, ZrO 2 , doped with Ce 4+ ions as surrogate for tetravalent Actinides in order to conclude on their long-term stability in deep geological underground. Both tetragonal and cubic yttrium-stabilized ZrO 2 (YSZ) exhibit excellent phase and structural stabilities up to 1150 K. In addition, incorporated guest Ce 4+ did not show any increase in their mobility at elevated temperatures. Application of external pressure did not induce any structural or phase changes in cubic YSZ doped with 5 at.% Ce as well. However, a corresponding tetragonal analog with lower yttrium content exhibits a second-order phase transition toward higher cubic symmetry around 9 GPa. Remarkably, no discharge of the guest Ce 4+ ions was observed throughout the transition and further upon increase in pressure. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the host YSZ matrices. The parent YSZ phases are, therefore, promising candidates as host materials for long-term underground immobilization for radiotoxic tetravalent elements like U, Th, or Pu.

Grazing-incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf beamline

“…Doped YSZ-based phases were also found to exhibit excellent stability at elevated temperatures with no discharge of incorporated guest tetravalent atoms (Svitlyk et al, 2022b). Similarly, application of external pressure did not induce changes in the chemical compositions of doped cubic and tetragonal YSZ phases, despite the phase transition induced in the tetragonal YSZ modification at 9 GPa (Svitlyk et al, 2022b). This shows the excellent affinity of incorporated tetravalent guest atoms with the host YSZ matrices under extreme temperature and pressure conditions.…”

“…Specifically, a more symmetrical arrangement of oxygen atoms in ZrO 8 polyhedra was found to result in a higher intake of tetravalent actinide elements. Doped YSZ-based phases were also found to exhibit excellent stability at elevated temperatures with no discharge of incorporated guest tetravalent atoms (Svitlyk et al, 2022b). Similarly, application of external pressure did not induce changes in the chemical compositions of doped cubic and tetragonal YSZ phases, despite the phase transition induced in the tetragonal YSZ modification at 9 GPa (Svitlyk et al, 2022b).…”

Additive Manufacturing of Zn‐Doped ZrO2Architectures

“…In Figure 4b 0 , the distinct sharp m-ZrO 2 reflections are recorded at 28.3°(À111) and 31.5°(111), with several mediumintensity reflections at 24.1°(011), 24 [54,56] The reflection at 30.3°is assigned to t-ZrO 2 (101), and several weaker signals of this phase might be shadowed around 35°and 50°. No peaks characteristic of ZnO wurtzite are found.…”

“…[2] Introducing substitutional impurities in the ZrO 2 crystal lattice is a promising route from a defect chemistry perspective. [6,[21][22][23][24] DOI: 10.1002/adem.202400187…”

Investigations towards incorporation of Eu3+ and Cm3+ during ZrO2 crystallization in aqueous solution

“…Mg 2+ , Ca 2+ , Fe 3+ , Y 3+ , La 3+ , Nb 5+ ) 3 , 8 – 14 and isovalent (e.g. Ce 4+ , Ti 4+ ) 15 , 16 cations. Incorporation of subvalent cations is accompanied by oxygen vacancy formation in the host structure to retain charge neutrality.…”