Higher hydride formation in lanthanides through mechanical milling

Superhydride compounds exhibit high temperature superconductivity due to the presence of high metal-to-hydrogen ratio, but only occur at very high formation pressures. Here we discuss how modifications of lanthanide precursors using mechanical ball milling prior to synthesis in a high-pressure diamond anvil cell can lead to a hydride phase with hydrogen content above that expected from the equilibrium phase diagram and improve hydrogen reactivity. Lanthanide precursors were subjected to a cryogenic ball milling technique and then exposed to a source of hydrogen in a diamond anvil cell. X-ray diffraction at HPCAT was used to explore the phase transformations of the metal hydride phase. We found an increase in hydrogen stoichiometry with mechanical ball milling relative to as received forms of lanthanide powders.