Oxygen non-stoichiometry of Ln {sub 4}Ni{sub 2.7}Fe{sub 0.3}O{sub 10-} {sub {delta}} (Ln=La, Pr)

Journal Article · Fri Jun 15 04:00:00 EDT 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2007.04.025· OSTI ID:21015853

Tsipis, E V ^[1]; Patrakeev, M V ^[2]; Waerenborgh, J C ^[3]; Pivak, Y V ^[1]; Markov, A A ^[2]; Gaczynski, P ^[3]; Naumovich, E N ^[1]; Kharton, V V ^[1]

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1. Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)
2. Institute of Solid State Chemistry, UB RAS, 91 Pervomaiskaya Str., 620219 Ekaterinburg (Russian Federation)
3. Chemistry Department, ITN/CFMC-UL, Estrada Nacional 10, P-2686-953 Sacavem (Portugal)

The oxygen deficiency of iron-substituted nickelates Ln {sub 4}Ni{sub 2.7}Fe{sub 0.3}O{sub 10-} {sub {delta}} (Ln=La, Pr) with the orthorhombic Ruddlesden-Popper structure was studied by thermogravimetric analysis and coulometric titration in the oxygen partial pressure range 6x10{sup -5} to 0.7 atm at 973-1223 K. In air, the non-stoichiometry values vary in the relatively narrow ranges (2.4-4.2)x10{sup -2} for La- and (0.01-2.0)x10{sup -2} for Pr-containing compositions, increasing with temperature. Due to the smaller size of praseodymium cations, Pr{sub 4}Ni{sub 2.7}Fe{sub 0.3}O{sub 10-} {sub {delta}} exhibits a substantially lower thermodynamic stability in comparison with La{sub 4}Ni{sub 2.7}Fe{sub 0.3}O{sub 10-} {sub {delta}} and La{sub 4}Ni{sub 3}O{sub 10-} {sub {delta}} , although the oxygen content in Pr{sub 4}Ni{sub 2.7}Fe{sub 0.3}O{sub 10-} {sub {delta}} lattice is higher. The partial substitution of iron for nickel has no essential effect on the low-p(O{sub 2}) stability limit corresponding to the transition of Pr{sub 4}Ni{sub 3}O{sub 10-} {sub {delta}} into K{sub 2}NiF{sub 4}-type Pr{sub 2}NiO{sub 4+} {sub {delta}} . On the contrary, doping of La{sub 4}Ni{sub 3}O{sub 10-} {sub {delta}} with iron decreases the oxygen vacancy concentration and shifts the phase stability boundary towards lower oxygen chemical potentials, suggesting a stabilization of the transition metal-oxygen octahedra in lanthanum nickelate lattice. The Moessbauer spectroscopy showed that the predominant state of iron cations, statistically distributed between the nickel sites, is trivalent. - Graphical abstract: Oxygen deficiency of Ruddlesden-Popper nickelates substituted with iron.

• OSTI ID: 21015853
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 6 Vol. 180; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
IRON COMPOUNDS
LANTHANUM COMPOUNDS
MOESSBAUER EFFECT
NICKEL COMPOUNDS
NICKELATES
ORTHORHOMBIC LATTICES
OXIDES
PARTIAL PRESSURE
PHASE STABILITY
PRASEODYMIUM COMPOUNDS
STABILIZATION
TEMPERATURE RANGE 1000-4000 K
THERMAL GRAVIMETRIC ANALYSIS
THERMODYNAMICS
TITRATION
VACANCIES