Effects of yttrium doping on helium behavior in zirconium hydride films

The zirconium hydride alloy films with different yttrium concentration were prepared by magnetron sputtering and studied using ion beam analysis (IBA), X-ray diffraction (XRD), thermal desorption spectrometry (TDS), positron annihilation spectroscopy (PAS) and nanoindentation. It was found that the yttrium atom, which is originally insoluble in zirconium metal, can largely dissolve in the zirconium hydride matrix through the introduction of hydrogen. The helium thermal desorption experiment shows that as the doped amount of yttrium atoms increases, a large number of helium atoms will be released in the form of helium bubbles at the grain boundaries in the matrix at ca. 900K. Combined with XRD results, it is concluded that as the yttrium atoms are introduced, more grain boundaries will form in the zirconium hydride matrix. These grain boundaries act as crystal defects, which have a strong trapping effect on helium atoms, causing a large number of helium bubbles to aggregate at the grain boundaries in the matrix. In addition, it is noteworthy that yttrium doping can increase the hardness and elastic modulus of zirconium hydride.