Abstract
La(3)Ni(2)O(7) differs from expectations in part because at ambient pressure, it exists in two polymorphs: an unconventional crystal structure with alternating layers of single- and triple-layered nickel-oxygen octahedra (i.e., La(2)NiO(4) plus La(4)Ni(3)O(10), with the so-called 1313 crystal structure) and a classical double-layer Ruddlesden-Popper phase (i.e., La(3)Ni(2)O(7), with the so-called 2222 crystal structure, which dominates at high pressure). In this study, we report the pressure-dependent structural and electrical resistive properties of single crystals of the classical double-layered La(3)Ni(2)O(7), grown at slightly elevated pressure using the floating-zone method. Structural characterization under pressures up to 15.4 GPa reveals a gradual transition from orthorhombic to tetragonal symmetry that is completed at 12-14 GPa. Additionally, we present pressure and field-dependent electrical resistance measurements up to 27.4 GPa, from which we construct a phase diagram. Although a resistive transition at 80 K is observed at high pressures, the resistive hallmarks of superconductivity are not.