A Hydride Route to Ternary Alkali Metal Borides: A Case Study of Lithium Nickel Borides

Ternary lithium nickel borides LiNi3B1.8 and Li2.8Ni16B8 have been synthesized by using reactive LiH as a precursor. This synthetic route allows better mixing of the precursor powders, thus facilitating rapid preparation of the alkali-metal-containing ternary borides. This method is suitable for "fast screening" of multicomponent systems comprised of elements with drastically different reactivities. The crystal structures of the compounds LiNi3B1.8 and Li2.8Ni16B8 have been re-investigated by a combination of single-crystal X-ray/synchrotron powder diffraction, solid-state Li-7 and B-11 NMR spectroscopies, and scanning transmission electron microscopy. This has allowed the determination of fine structural details, including the split position of Ni sites and the ordering of B vacancies. Field-dependent and temperature-dependent magnetization measurements are consistent with spin-glass behavior for both samples.