Hole and electron doping of RNiO{sub 3} (R = La, Nd)

Journal Article · Sat Apr 01 00:00:00 EST 1995 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1995.1196· OSTI ID:70191

Alonso, J A; Martinez-Lope, M J ^[1]; Hidalgo, M A ^[1]

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1. Instituto de Ciencia de Materials de Madrid (Spain)

The effect of hole and electron doping in the perovskites RNiO{sub 3} (R = rare earths) has been studied. R{sub 1-x}A{sub x}NiO{sub 3} (R = La, Nd; A = Sr, Th; O {le} x {le} 0.1) were prepared under 200 bars of oxygen and were characterized by X-ray and neutron powder diffraction, thermogravimetric analysis, differential scanning calorimetry, and resistivity measurements. The neutron data for rhombohedral La{sub 0.9}Sr{sub 0.1}NiO{sub 3} or orthorhombic Nd{sub 0.95}A{sub 0.05}NiO{sub 3} (A = Sr, Th) show that Sr or Th replace at random the rare-earth cations, whereas the oxygen positions remain fully occupied. NiO{sub 6} octahedra are either contracted, in the hole-doped Sr-containing samples, or expanded, in the electron-doped Th-containing compounds, as a consequence of the decrease/increase of the Ni-O bond lengths electronically induced by doping. Accordingly, bond-valence calculations give a valence for nickel higher/lower than +3, for the Sr/Th-doped compounds, respectively. The transport properties dramatically change with respect to the undoped compounds. The metal-to-insulator transition present in NdNiO{sub 3} (T = 200 K) disappears for Nd{sub 1-x}Sr{sub x}NiO{sub 3}, which remains metallic down to 1.5 K even for the smallest doping rate (5%). This fact can be structurally related to the straightening, by 1.4{degrees} for x = 0.05, of the (Ni-O-Ni) angles, which govern the transfer integral between Ni-3d and O-2p orbitals. For Nd{sub 0.95}Th{sub 0.05}NiO{sub 3} there is a suppression of the metal-insulator transition toward low temperatures (T = 132 K). Electronic factors, related to the injection of holes or electrons into the bands of the solid, are mostly responsible for the structural changes observed in these doped compounds, which cannot be explained by simple steric considerations.

• OSTI ID: 70191
• Journal Information: Journal of Solid State Chemistry, Vol. 116, Issue 1; Other Information: PBD: Apr 1995
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
LANTHANUM OXIDES
CRYSTAL DOPING
ELECTRIC CONDUCTIVITY
NEODYMIUM OXIDES
NICKEL OXIDES
THORIUM
STRONTIUM
THERMAL GRAVIMETRIC ANALYSIS
TRIGONAL LATTICES
HOLES
ELECTRONS
X-RAY DIFFRACTION
CALORIMETRY
ORTHORHOMBIC LATTICES
CRYSTAL STRUCTURE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K