Enhanced conductivity in Sr doped La₃Ni₂O_7-δ with high-pressure oxygen annealing

The structural, electrical and magnetic properties of a series of La_3-xSr_xNi₂O_7-δ polycrystalline samples have been systematically investigated with and without high-pressure oxygen annealing. Without annealing, the introduction of Sr at La site leads to a moderate enhancement of conductivity. The high-pressure oxygen annealing leads to an increase of oxygen content by ∼1.08 %. Consequently, the conductivity of the annealing samples is significantly enhanced comparing to the untreated samples. The La_3-xSr_xNi₂O_7-δ samples exhibit metal-like behavior in the whole temperature range with annealing, which is due to the hole doping effect. The present results could contribute to the exploration of possible ambient superconductivity in La₃Ni₂O_7-δ system.