Neutron irradiation effects on the microstructure of nuclear graphite have been investigated by X-ray diffraction on virgin and low doses (∼1.3 and ∼2.2 dpa), high temperature (750^° C) irradiated samples. The diffraction patterns were interpreted using a model, which takes into account the turbostratic disorder. Besides the lattice constants, the model introduces two distinct coherent lengths in the c-axis and the basal plane, that characterise the volumes from which X-rays are scattered coherently. The methodology used in this work allows to quantify the effect of irradiation damage on the microstructure of nuclear graphite seen by X-ray diffraction. The results show that the changes of the deduced structural parameters are in agreement with previous observations from electron microscopy, but not directly related to macroscopic changes.

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In-situ deposited YH2 films ranging from epitaxial to nanocrystalline were prepared by pulsed laser deposition (PLD). PLD has the advantage that the yttrium target acts as a hydrogen source. Comparing the switching behavior to that of MBE-grown, ex-situ loaded films, the PLD-films show a reduced optical and electrical contrast in switching, which is probably due to the formation of Y(OH)3. On the other hand, we found that in the nanocrystalline PLD-films the hysteresis in switching is absent. Moreover, these films have a smoother surface morphology. Both effects are important for the implementation of switchable rare earth hydride films in all-solid-state devices.@en

We prepared epitaxial YH2 films on (111) CaF2 by pulsed laser deposition (PLD) from a metallic yttrium target. Without adding any reactive hydrogen, the dihydride is formed in situ due to the hydrogen evolving from the metallic target which contains ~7 at% H. Upon pulsed laser irradiation, the target acts as a pulsed source of both yttrium and hydrogen. The increased hydrogen content of the film as compared to the target is explained to be due to diffusion assisted preferential ablation of hydrogen. Due to this deposition process the hydrogen load on the deposition system is minimized, which is important in view of the fabrication of hydride/oxide stacks for all-solid-state switchable mirror devices. Furthermore, the preparation of both nanocrystalline and epitaxial YH2 films shows the versatility of the PLD process.@en