High pressure equation of state and phase behavior of YbH_x nanoparticles

Hydride compounds are the subject of much investigation due to their relatively high superconducting temperatures, and nanoscale forms of materials are known to have different phase expression relative to their bulk counterparts. Therefore, we investigate whether a superhydride can be formed in ytterbium hydride nanoparticles. Ytterbium hydride nanoparticles were placed in diamond anvil cells to apply pressure during x-ray diffraction measurements to determine equation of state and crystal structure. In some cases, nanoparticle samples were placed alongside ammonia borane as a hydrogen source. The presence of ammonia borane appears to partially convert β-phase (Fmm) YbHx nanoparticles into α-phase (Pnma). Nanoparticles in the β phase appear to become amorphous at approximately 29 GPa, and α-phase nanoparticles may absorb hydrogen from ammonia borane when it is present at high pressure. Our results are compared with previously published data on bulk ytterbium hydride.