Structural effects of Sr substitution in La{sub 2{minus}x}Sr{sub x}NiO{sub 4+{delta}}

Journal Article · Fri May 01 00:00:00 EDT 1998 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.57.10370· OSTI ID:627830

Heaney, P J ^[1]; Mehta, A ^[2]; Sarosi, G; Lamberti, V E; Navrotsky, A ^[1]

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1. Princeton Materials Institute and Department of Geosciences, Princeton University, Princeton, New Jersey08544 (United States)
2. Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford, California94309 (United States)

Structures within the La{sub 2{minus}x}Sr{sub x}NiO{sub 4+{delta}} system (0{lt}x{le}1) were refined by Rietveld analysis of powder x-ray-diffraction data. Our results reveal three distinct regimes that parallel energetic transformations within the series. For 0{le}x{lt}0.2, enthalpies of oxidation are strongly exothermic and the compounds are monophasic and orthorhombic. Hole saturation occurs for 0.2{lt}x{lt}0.6, and the symmetry decreases from orthorhombic to monoclinic. For 0.6{lt}x{lt}1.0, diffraction patterns suggest phase immiscibility between a Sr-poor, hole-saturated compound and a Sr-rich phase for which oxidation is strongly favored. Fourier synthesis maps for all compositions revealed evidence for microtwinning and positional disorder among apical oxygen atoms. {copyright} {ital 1998} {ital The American Physical Society}

• OSTI ID: 627830
• Journal Information: Physical Review, B: Condensed Matter, Vol. 57, Issue 17; Other Information: PBD: May 1998
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
LANTHANUM OXIDES
STRONTIUM OXIDES
NICKEL OXIDES
CRYSTAL STRUCTURE
X-RAY DIFFRACTION
OXIDATION
REACTION HEAT
SYMMETRY
TWINNING
STOICHIOMETRY