The Structure and Properties of an Unusual New Nickel(III) Oxide: YSr 5Ni 3O 11

Abstract

An investigation of the system Y 2- x Sr x NiO 4-δ has shown that a stable phase exists only at x = 1.67 between 1100 and 1150°C. Thermogravimetric analysis gives the oxygen deficiency as δ = 0.33(1), showing that the phase is a stoichiometric nickel(III) oxide, YSr 5Ni 3O 11 (Y 0.33Sr 1.67NiO 3.67). Rietveld refinement using powder X-ray diffraction data confirms that YSr 5Ni 3O 11 adopts the tetragonal K 2NiF 4 (T-type) structure ( I4/ mmm, Z = 2 3 , a = 3.7762(1), c = 12.3011(4) Å, R wp = 3.9%). Independent refinement of the oxygen site occupancies reveals that the oxygen vacancies are present in the nickel oxide planes. Magnetic susceptibility data for YSr 5Ni 3O 11 at 5-350 K show Curie-Weiss behavior characteristic of low spin Ni 3+ with μ eff = 1.76 and Θ = - 10.8 K. Four-probe dc electronic conductivity measurements show that the material is a semiconductor between 7 and 300 K. These data are well fitted by a two-dimensional variable range hopping model.