On the relationships between structure, oxygen stoichiometry and ionic conductivity of CaTi1−xFexO3−δ (x=0.05, 0.20, 0.40, 0.60)

Figueiredo, F. M.; Waerenborgh, J.C.; Хартон, В.В.; Näfe, H.; Frade, J.R.

doi:10.1016/s0167-2738(02)00762-2

Cited by 44 publications

(35 citation statements)

References 13 publications

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“…88.8 kJ/mol for x=0.2 and 93.6 kJ/mol for x=0 (9). Such difference may be related to the fraction of tetravalent iron, which is expected to be higher at low temperature (20) thus facilitating the hopping of small polarons between Fe 4+ and Fe…”

Section: Model Behaviourmentioning

confidence: 99%

Procesamiento y conductividad eléctrica de galato de lantano con heteroestructura de tipo core-shell

Gomes¹,

Figueiredo²,

Marques³

2006

Bol. Soc. Esp. Ceram. Vidr.

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The electrical properties of a lanthanum gallate solid electrolyte were modified by selectively doping the grain boundaries with Fe. This was achieved by sandwiching a La 0.95 Sr 0.05 Ga 0.90 Mg 0.10 O 3-δ (LSGM) dense pellet between LaFeO 3 samples. Annealing at 1550°C in air for several hours promoted Fe diffusion into LSGM via the grain boundaries. Scanning electron microscopy and energy-dispersive spectroscopy analyses showed that iron was located at the grain boundary while the grain bulk preserved the LSGM composition. Impedance spectra obtained at low temperature consist of the two usual bulk and grain boundary contributions. A significant increase in total conductivity was observed for the iron-doped samples, the effect being greater for the grain boundary contribution. The total conductivity measured for the iron-containing material revealed a slight decrease with decreasing oxygen partial pressure, suggesting the onset of p-type electronic conduction. Estimates of the p-type electronic conductivity (σ p ) were obtained by fitting the low temperature impedance spectra to a simple equivalent circuit including one parallel electronic branch. The value for σ p in air at 300°C is 3.1×10 -6 S/cm and the activation energy is 75.1 kJ/mol between 300 and 400°C.Keywords: core-shell, gallate, grain boundary, mixed conductor, impedance spectroscopy. Procesamiento y conductividad eléctrica de galato de lantano con heteroestructura de tipo core-shell.Las propiedades elécticas de un electrolito sólido de galato de lantano se han modificado mediante un dopado eléctrico de Fe en borde de grano. Esto se consiguió preparando una estructura de sandwich con una plantilla densa de La 0.95 Sr 0.05 Ga 0.90 Mg 0.10 O 3-δ (LSGM) entre las muestras de LaFeO3. Un tratamiento de varias horas a 1550ºC en aire favoreció la difusión de Fe a lo largo de los bordes de grano. Los análisis mediante microscopia electrónica de barrido y espectroscopía de energía dispersada muestran que el hierro se localiza en borde de grano mientras que se preserva la composición de LSGM en el interior de grano. En las muestras dopadas con hierro se observa un aumento de la conductividad total siendo el efecto más notable en el borde del grano. La conductividad total del material que contiene hierro presentó un ligero descenso al reducirse la presión parcial de oxígeno, lo que sugiere la presencia de conducción electrónica tipo p. La conductividad electrónica tipo (σ p ) se evaluó ajustando el espectro de impedancia de baja temperatura a un circuito equivalente sencillo con una resistencia electrónica en paralelo. El valor de σ p en aire a 300ºC es 3,1×10 -6 S/cm y la energía de actuación 75,1 kJ/mol entre 300 y 400ºC.Palabras clave: core-shell, galato, borde de grano, conductor mixto, espectroscopía de impedancia.

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Section: Model Behaviourmentioning

confidence: 99%

Procesamiento y conductividad eléctrica de galato de lantano con heteroestructura de tipo core-shell

Gomes¹,

Figueiredo²,

Marques³

2006

Bol. Soc. Esp. Ceram. Vidr.

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“…The planetary rotation was kept constant at 650 rpm and the container at 1300 rpm, in the opposite direction. Powder XRD patterns revealed a perovskite forming from the early milling stages and a completed reaction after 180 min, with no apparent crystalline or amorphous intermediates, indicating significant Mn solubility in CaTiO 3 . Patterns show a decrease in lattice volume upon Mn substitution, as expected from the lower Mn 3+ or Mn 4+ ionic radii when compared to Ti…”

Section: Mechanosynthesis Of Nanocrystalline Cati 1-x Mn X O 3-δmentioning

confidence: 99%

“…It is well-known that the partial substitution of Ti 4+ by Fe transforms the incipient ferroelectric CaTiO 3 into a good oxygen ionic/electronic mixed conductor (1)(2)(3)(4) ) and reasonably good transport properties, and were thus envisaged for application as membranes for electrochemical oxygen separation (9) or hydrogen production. (10) Nevertheless, the ionic transport is recognised to be somewhat limited and any improvement of this characteristic is important for the actual technological application of the material.…”

Section: Introductionmentioning

confidence: 99%

Mecanosíntesis de polvos nanocristalinos de CaTi1-xMnxO3-Î´

Gonçalves¹,

Vázquez²,

M.³

2008

Bol. Soc. Esp. Ceram. Vidr.

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La mecanosíntesis de CaTi 1-x Mn x O 3-δ nanocristalino es presentada por primera vez. Polvos reactivos de CaO, TiO 2 anatasa y Mn 2 O 3 (Aldrich) fueron pesados en las cantidades estequiométricas adecuadas para obtener CaTi 1-x Mn x O 3-δ (x=0. 05, 0.10, 0.15, 0.20, 0.30, 0.50 y 0.80) por molienda en seco en un molino planetario de alta energía utilizando contenedores y bolas de circona, en una relación masa de bolas : masa de polvo de 10:1. La rotación del planetario se mantuvo constante a 650 revoluciones por minuto (rpm) y la del contenedor a 1300 rpm, en el sentido inverso. La formación de una fase con estructura de perovskita fue identificada a través del análisis de los polvos por difracción de rayos X, siendo esta fase claramente mayoritaria en los polvo molidos durante 180 min y sin observarse la formación de compuestos intermediarios. Los patrones de difracción de rayos X también indicaron una disminución de los parámetro de red con el aumento del contenido en Mn, en acuerdo con el menor rayo iónico de Mn 3+ o Mn 4+ comparado con el del catión Ti 4+. El tamaño medio de los cristales fue estimado entre 5 y 30 nm a partir de gráficos de Williamson-Hall y confirmado por microscopia electrónica de transmisión. Palabras clave: Conductor mixto, titanato, mecanosíntesis. Mechanosynthesis of nanocrystalline CaTi 1-x Mn x O 3-δThe mechanosynthesis of nanocrystalline CaTi 1-x Mn x O 3-δ is reported for the first time. Powdered CaO, TiO 2 anatase and Mn 2 O 3 (Aldrich) were weighed in the appropriate stoichiometric quantities in order to obtain CaTi 1-x Mn x O 3-δ (x=0.05, 0.10, 0.15, 0.20, 0.30, 0.50 and 0.80) and dry milled in a planetary high-energy ball mill, using zirconia containers and balls, with a 10:1 ball/ mass ratio. The planetary rotation was kept constant at 650 rpm and the container at 1300 rpm, in the opposite direction. Powder XRD patterns revealed a perovskite forming from the early milling stages and a completed reaction after 180 min, with no apparent crystalline or amorphous intermediates, indicating significant Mn solubility in CaTiO 3 . Patterns show a decrease in lattice volume upon Mn substitution, as expected from the lower Mn 3+ or Mn 4+ ionic radii when compared to Ti 4+ . The average crystallite size is in the range 5-30 nm, as determined from Williamson-Hall plots and confirmed by high resolution transmission electron microscopy.

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“…Apart from the protonic and electronic conductivity the doped perovskite shows also oxygen-ion conductivity [15][16][17][18]. Furthermore the compatibility of the cathode material with the electrolytes and interconnectors is crucial for cathode material.…”

Section: Introductionmentioning

confidence: 99%

INFLUENCE OF PORE FORMERS ON ELECTRICAL PROPERTIES OF CaTi0.9Fe0.1O3-δ PEROVSKITE-TYPE CERAMICS

Lendze¹,

Mielewczyk‐Gryń²,

Gdula-Kasica³

et al. 2011

Advances in Materials Sciences

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Porous CaTi 0.9 Fe 0.1 O 3-δ (CTF) perovskites were synthesized by the standard solid state method at different sintering temperatures with carbon black (CB), corn starch (CS) and potato starch (PS) as pore-forming agents. The ceramic samples of porosity between 9% and 42% with 5 -40 µm pore sizes, were obtained by a 6 h sintering at either 1130º C or 1200º C of precursor powder prepared at 1470º C. X-ray diffraction analysis proved the existence of orthorhombic single-phase perovskites crystalline structure. Electrical conductivity at 800° C was between 1.42 ×10 −2 S cm −1 and 1.86×10 −3 Scm −1 . The conductivity markedly depended on the sample porosity. It should be noted that 30% of porosity, resulted in reduction of conductivity by less than one order of magnitude. Activation energy of conductivity varied between 0.41 and 0.56 eV. Cornstarch has been chosen as the most suitable pore-forming agent for obtaining the cathode of good properties. The best amount of the cornstarch has been proposed as between 5 and 10%.

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On the relationships between structure, oxygen stoichiometry and ionic conductivity of CaTi1−xFexO3−δ (x=0.05, 0.20, 0.40, 0.60)

Cited by 44 publications

References 13 publications

Procesamiento y conductividad eléctrica de galato de lantano con heteroestructura de tipo core-shell

Procesamiento y conductividad eléctrica de galato de lantano con heteroestructura de tipo core-shell

Mecanosíntesis de polvos nanocristalinos de CaTi<sub>1-x</sub>Mn<sub>x</sub>O<sub>3-Î´</sub>

INFLUENCE OF PORE FORMERS ON ELECTRICAL PROPERTIES OF CaTi0.9Fe0.1O3-δ PEROVSKITE-TYPE CERAMICS

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