Understanding Transient Kinetics under Irradiation with In Situ EIS

Particle irradiation introduces a large amount of energy into a material, creating a multitude of metastable defect structures. These defects are then responsible for the microstructural evolution of the material, which often comes down to a balance of kinetic processes that determine whether the material will recover or whether larger-scale defect aggregates such as voids and loops will form. Critically, the defects most responsible for this evolution – the fastest moving defects – disappear quickly once the radiation source is removed. Thus, post-mortem examination can only provide indirect evidence of their presence and is unable to characterize neither the nature nor properties of these defects.<br/><br/>To better understand the transient behavior associated with fast moving radiation-induced defects, we have developed an in situ electrochemical impedance spectroscopy system that allows us to measure the conductivity of the material as it is being irradiated. This provides unprecedented insight into the kinetic nature of defects, both as the material approaches a steady-state defect concentration under irradiation and as it recovers once the irradiation source is removed.<br/><br/>We demonstrate this new capability on complex oxides. For example, in yttrium-stabilized zirconia, we find that there is an enhancement of the conductivity of the material during irradiation, leading to an effectively lower activation energy for conduction as the material is being irradiated. However, once the radiation source is turned off, the conductivity quickly recovers to the pre-irradiated value, emphasizing the critical need for in situ diagnostics to probe the properties of these transient defects.