Elusive superconductivity in polycrystalline samples of layered lanthanum nickelates

La 2-x NiO 4, La 2-x Sr x NiO 4 and related layered nickelates have been investigated for possible presence of superconductivity. While there is clear onset of diamagnetism around 20 K in many of these nickelates, we do not, however, find any anomaly in the electrical resistivity, magnetoresistance or thermopower around 20 K. High energy spectroscopic studies show Ni to be in the 2+ oxidation state accompanied by a substantial proportion of oxygen holes.