Exploration and optimization of ZrCo(Ti) type film for high hydrogen density and thermal stability of the hydride

Abstract Tritium target is of crucial importance in relation to the development of neutron generator apparatus. However, the prevalent Ti target is now suffering from the intricate procedures for activation, limited tritium content at room temperature (RT) and poor ability to fix the helium. Herein, a succession of new type ZrCo(Ti) alloy targets were designed and fabricated by magnetron sputtering. Firstly, the influence of technological parameters (types of substrate, sputtering temperatures, sputtering time and annealing temperatures) on the assemblage and also the hydrogen storage properties of the ZrCo films were systemically studied. The results show that high sputtering temperature is benefit to acquiring high crystallinity of ZrCo films, but the substrates seem to have no significant effect on that. The thickness and grain size of ZrCo film are both positively related to the sputtering time. However, the hydrogen uptake capacities (0.14 wt%~0.79 wt%) for all the prepared ZrCo films are relatively low. After that, the composition and microstructure of the ZrCo films were further regulated and optimized. On the one hand, Zr1-xTixCo films were constructed by introduction of Ti element, achieving a higher hydrogen absorption capacity (~0.7 wt%), but with weak thermal stability in the subsequent hydrogen desorption process (~80% of hydrogen escaped at 500 °C). On the other hand, the surface of the ZrCo film was modified by a thin layer of Ti, forming a serious of double-layer ZrCo/Ti films. The ZrCo/Ti composite films not only achieve extremely high hydrogen storage capacity (1.85 wt%), but also maintain strong thermal stability (only 15.7% of hydrogen escaped at 500 °C). These findings related to the ZrCo(Ti) films in this paper provide crucial reference for the development of tritiated ZrCo film targets, and spark inspiration even for the design of other new-type tritiated film target.