Abstract
Irradiation induced damage in materials is highly detrimental and is a critical issue in several vital science and technology fields, e.g., the nuclear and space industries. While the effect of dimensionality (nano/bulk) of materials on its radiation damage tolerance has been receiving tremendous interest, studies have only concentrated on low energy (nuclear energy loss (Sn) dominant) and high energy (electronic energy loss (Se) dominant) irradiations independently (wherein, interestingly, the effect is opposite). In-fact, research on radiation damage in general has almost entirely focused only on independent irradiations with low and/or high energy particles till date, and investigations under simultaneous impingement of energetic particles (which also correspond to the actual irradiation conditions during real-world applications) are very scarce. The present work elucidates, taking cubic zirconia as a model system, the effect of grain size (26 nm vs 80 nm) on the radiation tolerance against simultaneous irradiation with low energy (900 keV I) and high energy (27 meV Fe) particles/ions; and, in particular, introduces the enhancement in the radiation damage tolerance upon downsizing from bulk to nano dimension. This result is interpreted within the framework of the thermal-spike model after considering (1) the fact that there is essentially no spatial and time overlap between the damage events of the two ‘simultaneous’ irradiations, and (2) the influence of grain size on radiation damage against individual Sn and Se. The present work besides providing the first fundamental insights into how the grain size/grain boundary density inherently mediates the radiation response of a material to simultaneous Sn and Se deposition, also (1) paves the way for potential application of nano-crystalline materials in the nuclear industry (where simultaneous irradiations with low and high energy particles correspond to the actual irradiation conditions), and (2) lays the groundwork for understanding the material behaviour under other simultaneous (viz. Sn and Sn, Se and Se) irradiations.
Highlights
The micron sized S1300 sample can be considered as bulk, while S600 is nanosized. The phase of both S600 and S1300 was verified to be the cubic phase from XRD and Raman spectroscopy (Supplementary Information)
Since grain boundaries (GBs) are defect sinks, the defects that are produced in the collision cascades upon the Sn irradiations are trapped by them (directly in the collision cascades and as well as because of thermal migration from nearby regions to the G Bs15,28) which results in their removal/reduction
This process of defect removal/reduction by the GBs is much more efficient in S600 as compared to S1300 because: (1) the volume fraction of GBs is higher in the S600 sample, and (2) the possibility of the irradiation induced collision cascades occurring ‘near’ the GBs is higher and the defects can more interact with the GBs
Summary
Sample preparation. 10 mol% yttria stabilized zirconia (YSZ) powder was prepared by gel combustion method (see Ref.[38] for details) and compacted into pellets of diameter ~ 8 mm. The S600 and S1300 samples were simultaneously irradiated with 27 MeV Fe ions (Se dominant) and 900 keV I ions ( Sn dominant) at the JANNUS-Saclay facility[40,41]. The fluence of both the ion species was 1015 ions/cm[2]; the irradiations were performed at room temperature with the ion fluxes limited to ~ 1011 ions/cm2/sec. During the simultaneous irradiations, only the region up-to a depth of ~ 240 nm is affected by both 27 MeV Fe (Se) and 900 keV I (Sn). It is worth mentioning explicitly that since the focus of the manuscript is the investigation of the radiation damage under simultaneous Se and Sn deposition, the region irradiated by both the Fe and I ions is of interest and relevance
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