Electrical and magnetic properties of La2−xSrxNiO4: A tentative phase diagram

La2−xSrxNiO4 shows a maximum in the c / a ratio around x = 0.6 up to which composition the concentration of holes is equal to that expected theoretically. The material becomes a degenerate semiconductor above a certain temperature up to x = 0.8, but is metallic at room temperature when x ⩾ 1.0. All the compositions with x ⩾ 0.05 are paramagnetic in the 15 - 300K range. Based on these measurements, an electronic phase diagram is tentatively proposed. It is noteworthy that the antiferromagnetic order disappears at low doping levels in both La2−xSrxNiO4 and La2−xSrxCuO4, but metallicity is seen at 300K only at a much higher x value in the former system.