Structural response of Nd-stabilized zirconia and its composite under extreme conditions of swift heavy ion irradiation

Inert matrix fuel concept for minor actinide transmutation proposes stabilized zirconia as the major component for inert matrix. The present study explores Nd-stabilized zirconia (Zr_0.8Nd_0.2O_1.9; Nd as surrogate for Am) and its composites for radiation tolerance against fission fragments. The introduction of MgO in the composite with stabilised zirconia is performed from the point of view to enhance the thermal conductivity. The radiation damage is also compared with Nd-stabilized zirconia co-doped with Y³⁺ (Zr_0.8Nd_0.1Y_0.1O_1.9) in order to mimic doping of minor actinides in Y³⁺ containing stabilized zirconia (Nd as surrogate for Am). The compositions were synthesized by gel combustion followed by high temperature sintering and characterised by XRD, SEM and EDS. Irradiation was carried out by 120 MeV Au ions at various fluences and irradiation induced structural changes were probed by in-situ X-ray diffraction (XRD). XRD demonstrated the retention of crystallinity for all the three samples but the extent of the damage was found to be highly dependent on the nominal composition. It was observed that introduction of Y³⁺ along with Nd³⁺ to stabilize cubic zirconia imparted poorer radiation stability. On the other hand, formation of a CERCER composite of MgO with Nd-stabilised zirconia enhanced its behaviour against swift heavy ion irradiation. Investigating these compositions by XANES spectroscopy post irradiation did not show any change in local electronic structure of constituent ions.