Chemical and structural changes in Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) lanthanide nickelates as a function of oxygen partial pressure at high temperature

Journal Article · Sat Aug 15 00:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.04.029· OSTI ID:22486736

Flura, Aurélien; Dru, Sophie; Nicollet, Clément; Vibhu, Vaibhav; Fourcade, Sébastien; Lebraud, Eric; Rougier, Aline; Bassat, Jean-Marc; Grenier, Jean-Claude

The chemical stability of lanthanide nickelates Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) has been studied in the temperature range 25–1300 °C, either in air or at low pO{sub 2} (down to 10{sup −4} atm). Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterization have shown that all compounds retain their K{sub 2}NiF{sub 4}-type structure in these conditions, while remaining over-stoichiometric in oxygen up to 1000 °C. Only Nd{sub 2}NiO{sub 4+δ} starts to decompose into Nd{sub 2}O{sub 3} and NiO above 1000 °C, at pO{sub 2}=10{sup −4} atm. In addition, a careful analysis of the lanthanide nickelates structural features has been performed by in situ XRD, as a function of temperature and pO{sub 2}. For all compounds, a structural transition has been always observed in the temperature range 200–400 °C, in air or at pO{sub 2}=10{sup −4} atm. In addition, their cell volume did not vary upon the variation of the oxygen partial pressure. Therefore, these materials do not exhibit a chemical expansion in these conditions, which is beneficial for a fuel cell application as cathode layers. Additional dilatometry measurements have revealed that a temperature as high as 950 °C for Pr{sub 2}NiO{sub 4+δ} or 1100 °C for La{sub 2}NiO{sub 4+δ} and Nd{sub 2}NiO{sub 4+δ} has to be reached in order to begin the sintering of the material particles, which is of primary importance to obtain an efficient electronic/ionic conduction in the corresponding designed cathode layers. Besides, excellent matching was found between the thermal expansion coefficients of lanthanide nickelates and SOFC electrolytes such as 8wt% yttria stabilized zirconia (8YSZ) or Ce{sub 0.8}Gd{sub 0.2}O{sub 2−δ} (GDC), at least from 400 °C up to 1400 °C in air or up to 1200 °C at pO{sub 2}=10{sup −4} atm. - Graphical abstract: This study reports the good chemical stability of oxygen overstoichiometric Ln2NiO4+δ(Ln = La, Pr or Nd) at high temperatures (up to 1300 °C), eitherin air or at pO2down to 10-4 atm. In addition, these MSC cathode materials show a small chemical expansion as well as a good TEC compatibility with electrolyte materials (GDC or YSZ). - Highlights: • The structure of Ln2NiO4+δ compounds are studied vs. temperature and pO2 • Structural transitions are evidenced in air as well as in low pO2 atmosphere • The structural transitions do not significantly affect their TECs values • Up to 1200 °C, they show good chemical stability and no chemical expansion vs. pO2 • TECs of nickelates, 8YSZ and GDC are compared in air and in low pO2 atmosphere.

• OSTI ID: 22486736
• Journal Information: Journal of Solid State Chemistry, Vol. 228; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ATMOSPHERES
DILATOMETRY
GRAVIMETRY
LANTHANUM COMPOUNDS
LAYERS
NEODYMIUM OXIDES
NICKEL OXIDES
NICKELATES
PARTIAL PRESSURE
PRASEODYMIUM COMPOUNDS
PRESSURE DEPENDENCE
SINTERING
SOLID OXIDE FUEL CELLS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
THERMAL EXPANSION
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION
YTTRIUM OXIDES
ZIRCONIUM OXIDES