Synthesis and Characterization of Pure Infinite Layer Ni + Nickelates: LnNiO 2 (Ln = La, Nd, Pr) and La 3 Ni 2 O 6

Abstract

A synthesis method of pure low valence nickelates using a custom built H 2 circulation apparatus is described. Pure infinite layer LnNiO 2 (Ln = La, Nd, Pr) and La 3 Ni 2 O 6 nickelates have been successfully prepared using this method and characterized by x-ray diffraction. Resistivity of La 3 Ni 2 O 6 was measured as a function of temperature and pressure up to ∼2 GPa and revealed significant pressure-induced changes in both magnitude and pressure dependence of resistivity. The existence of a hidden insulator-metal transition in La 3 Ni 2 O 6 is proposed at pressures above 100 GPa.