Micro and macro damage defects in heavy-ion irradiated MgO-Nd2Zr2O7 composite ceramics used for inert matrix fuel

In this work, the heavy-ion irradiation responses of MgO-Nd2Zr2O7 (M-NZO) composite ceramics used for inert matrix fuel were experimentally investigated. And the micro and macro radiation damage of M-NZO samples was systemically unveiled after 5 MeV Xe20+ irradiation and quantified by two exposure units, displacements per atom (dpa) and phonons per atom (ppa). The newly ppa represent the number of phonon modes available in the radiated material, which are high relative to thermal properties and the resulting morphological fragmentation after irradiation. In detail, MgO phase mostly retains its pristine structure without extensive amorphization irradiated at high dpa values, meanwhile, Nd2Zr2O7 phase also presents satisfactory radiation resistance through the distinctive order-disorder structural transformations that alleviate radiation-induced strain. Besides, MgO grains with lower ppa value dissipate ions energy more efficiently than Nd2Zr2O7, and exhibit higher radiation tolerance at macroscopic morphological scale. Overall, M-NZO composite ceramics have good radiation tolerance under heavy-ion bombardment, in which the lower ppa value and higher thermal conductivity of MgO make itself possess superior resistance to irradiation-induced damage than Nd2Zr2O7.