Correlation between electrical properties and thermodynamic stability of ACoO{sub 3-{delta}} perovskites (A= La, Pr, Nd, Sm, Gd)

Journal Article · Mon Aug 15 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.085113· OSTI ID:21596856

Scherrer, Barbara; Harvey, Ashley S; Martynczuk, Julia; Gauckler, Ludwig J ^[1]; Tanasescu, Speranta; Teodorescu, Florina; Botea, Alina ^[2]; Conder, Kazimierz ^[3]; Grundy, A Nicholas ^[1]

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1. Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland)
2. Institute of Physical Chemistry ''Ilie Murgulescu,'' Splaiul Independentei 202, 060021 Bucharest (Romania)
3. Laboratory for Developments and Methods, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland)

For perovskites with the general formula ACoO{sub 3-{delta}} (A = La, Pr, Nd, Sm, and Gd) the influence of the A-site cation on the electrical conductivity, electronic structure, thermodynamic stability, and oxygen stoichiometry was studied. The perovskite oxide powders were produced by a combined citric acid and ethylenediaminetetraacetic acid complexing method. Ceramic specimens sintered at 1100 deg. C in air were single-phase perovskites. With increasing temperature, the electrical conductivity shows three discrete regimes. All compositions show semiconductivity up to a transition temperature of {approx}300 deg. C-450 deg. C and then behave like metallic conductors. The activation energies for the semiconductivity, as well as the transition temperatures to the metallic-like conduction, decrease monotonically with increasing pseudocubic lattice parameters, i.e., with increasing ionic radii of the A cation. This behavior correlates with decreasing oxygen nonstoichiometry and increased thermodynamic stability. The highest conductivity and the lowest activation energy of 0.66 eV were found for LaCoO{sub 3-{delta},} which also had the lowest semiconductor-metal transition temperature at 269 deg. C, the lowest oxygen nonstoichiometry of {delta}= 0.008, and the highest Gibbs free energy change for the decomposition reaction of 42.37 kJ/mol at 850 deg. C. GdCoO{sub 3-{delta}} had the highest oxygen nonstoichiometry with {delta}0.032, a high activation energy of 1.19 eV for the semiconductivity with a high transition temperature at 452 deg. C, and the lowest Gibbs free energy change of 26.54 kJ/mol at 850 deg. C. X-ray absorption spectroscopy data imply an increasing Co low-spin character with decreasing cation radius from La to Gd, while an increase in temperature increases the number of holes or Co 3d bandwidth. This correlates well with the electrical conductivity data.

• OSTI ID: 21596856
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 84, Issue 8; Other Information: DOI: 10.1103/PhysRevB.84.085113; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
CERAMICS
COBALT COMPOUNDS
CORRELATIONS
ELECTRIC CONDUCTIVITY
ELECTRONIC STRUCTURE
EV RANGE
FREE ENTHALPY
GADOLINIUM COMPOUNDS
LANTHANUM COMPOUNDS
LATTICE PARAMETERS
NEODYMIUM COMPOUNDS
OXYGEN
OXYGEN COMPOUNDS
PEROVSKITE
PRASEODYMIUM COMPOUNDS
SAMARIUM COMPOUNDS
SEMICONDUCTOR MATERIALS
STABILITY
STOICHIOMETRY
TEMPERATURE RANGE 0400-1000 K
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
X-RAY SPECTROSCOPY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY
ENERGY RANGE
MATERIALS
MINERALS
NONMETALS
OXIDE MINERALS
PEROVSKITES
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SPECTROSCOPY
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS