Synthesis of cubic lutetium hydride at HPHT conditions and its implications
Abstract
Binary rare earth hydrides are ideal hydrogen rich materials for the search of room temperature superconductivity. Even though there are plethora of such theoretical predictions, only a few binary hydrides show high T C experimentally. The recent progress in the search for new ternary hydrides have led to the controversial discovery of room temperature superconductivity in the nitrogen doped lutetium hydride (LuH 3- delta N epsilon ) (NLH). This has stimulated the interest in the synthesis of lutetium hydrides and their detailed understanding. Phase pure LuH 2 has been synthesized using pure Lutetium (Lu) metal and paraffin as hydrogen source at high pressure and high temperature conditions. The sample inside diamond anvil cell (DAC) has been characterised with optical micrographs using high resolution optical microscope. The recovered sample is characterised by employing synchrotron based angle dispersive x-ray diffraction (ADXRD) measurements. The lattice parameter of as synthesized LuH 2 is in excellent agreement with the earlier reported one. The comparison of high pressure evolution of the unit cell volumes of synthesized LuH 2 , cubic LuH 3 and NLH imparts broader understanding and opens the way for future research in lutetium based hydride systems. Data analysis at high pressures reveals that the parent structural framework of NLH is LuH 2 rather than LuH 3 . Here, we have proposed a novel method for determination of hydrogen stoichiometry in ternary rare earth hydride systems. In this method, hydrogen to metal ratio (H:M) and metal-hydrogen (M - H) distance as a function of hydrogen-solubilities systematics for lanthanide dihydrides solid solution are utilized to constrain the concentration of hydrogen in these compounds.
