Mat. Res. Bull., Vol. 25, pp. 293-306, 1990. Printed in the USA. 0025-5408/90 $3.00 + .00 Copyright (c) 1990 Pergamon Press plc. CRYSTAL CHEMISTRY AND PHYSICAL PROPERTIES OF La2_xSrxNi04(O < x J 1.6) Y. Takeda, R. Kanno, M. Sakano, and O.Yamamoto Department of Chemistry, Faculty of Engineering, Mie University Tsu, Mie-ken, 514, Japan M.Takano, and Y. Bando Institute for Chemical Research, Kyoto University Uji, Kyoto-fu 611, Japan H. Akinaga, and K. Takita Institute of Materials Science, University of Tsukuba Tsukuba City, Ibaragi-ken, 305, Japan J.B. Goodenough University of Texas at Austin, ETC 5. 160, Austin TX 78712-1084, USA (Received September 25, 1989; Communicated by M. Koizumi) ABSTRACT Structural, transport, and magnetic data for the system La2_xSrxNi04, 0 ! × J 1.6, are reported. The oxygen content of the system was controlled by annealing under various oxygen partial pressures below 150 atm and was determined by iodometric titration. A Rietveld analysis of the room- temperature powder X-ray diffraction data showed that the tetragonal distortion of the NiO 6 octahedra decreases monotonically with increasing x for 0 ~ x ! 1.4, but the La(Sr)-O(2) bond length increases anomalously in the interval 0 J x J 0.6. A semiconductor-metal transition decreases monotonically with increasing x from about 675 K(x=O) to 20 K(x=l.2). Samples with x > 1.0 exhibited a weak ferromagnetic moment at 5 K and the onset of a positive component in the Hall effect. Comparison of the La2_xSrxCuO 4 and La~ Sr NiO, systems shows that the superconductive copper z-x x ~ 3+ 2 2+ oxides have the equilibrium Cu + 0 - = Cu + O- shifted to the right and, for x = O, antiferromagnetic correlation in a half-filled Ox2 y2 band - 4+ whereas the weakly ferromagnetic: nickel oxides have the equilibrium Nl + 02- = Ni 3+ + O- shifted to the right, but ferromagnetic correlations in a quarter-filled d ~ band. MATERIAL INDEX: lanthanum, strontium, nickel, oxides 293