Electronic excitation driven structural evolution in Ce0.8Zr0.2O2

Abstract

The cubic phasic CeO2–ZrO2 system with the composition Ce0.8Zr0.2O2 has been synthesized at room temperature. Highly dense pellets were synthesized by standard solid-state route. Fluorite structured cubic phase was probed by X-ray diffraction along with a qualitative analysis through Rietveld refinement. A ‘pseudocubic’ phase of pristine material was noted experimentally by Raman vibrational modes corresponding to anionic displacement in cubic phase and theoretically explained as the tetragonal anionic arrangement (P42/nmc) at nanoscale embedded in framework of cubic structure (Fm3‾m). Electron microscopy accompanied by density measurement was employed to conclude that the synthesized ceramic has a very compact surface morphology with a density ∼95% of its theoretical value. The as-prepared pellets were irradiated with 100 MeV I7+ ions to mimic energy loss by fission fragment during reactor operation. A comprehensive investigation of structural damage was done through the analysis of diffraction patterns of irradiated samples. We carefully estimated the damaged regions with diameter as ∼3.18 nm and ∼2.54 nm from irradiation induced peak broadening and lattice swelling, respectively. These results are fully capable to conceptualize a model about the damaged cylindrical region along ion trajectory. A central region (∼2.54 nm) consists of extended defects revealed by lattice swelling. Moreover, an annular region (width ∼0.32 nm) consists of vacancy type simple defects accommodated in as-synthesized lattice structure. These results reveal excellent structural properties of CeO2–ZrO2 modelled system comparable to PuO2−ZrO2.