Influence of Microstructure on the Electrical Properties of Iron‐Substituted Calcium Titanate Ceramics

Figueiredo, F. M.; Хартон, В.В.; Waerenborgh, J.C.; Viskup, A.P.; Naumovich, E.N.; Frade, J.R.

doi:10.1111/j.1151-2916.2004.tb07501.x

Cited by 33 publications

(37 citation statements)

References 45 publications

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“…The most common approach to these composites is a simple two-phase mixture of contiguous grains (10,11 (15). Interestingly, the oxygen permeability flux (and thus the ionic conductivity) measured for the heterogeneous ceramics is considerably higher than the compositionally identical CaTi 0.8 Fe 0.2 O 3-δ homogeneous material.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…Among them, iron-doped calcium titanate CaTi 1− Fe O 3 (CTF) has been considered as a candidate for a cathode material for proton-conducting SOFCs with lanthanum niobate as an electrolyte [4]. Acceptor-doped lanthanum niobate (LNO) and iron-doped calcium titanate are one of the unconventional electrolyte and cathode materials, respectively, because they have a relatively low conductivity [5]. One of the main advantages of lanthanum niobates is their stability in CO 2 atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Characterization of CaTi0.9Fe0.1O3/La0.98Mg0.02NbO4 composite

et al. 2013

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Abstract:A composite of CaTi 0 9 Fe 0 1 O 3 and electrolyte material, i.e. magnesium doped La 0 98 Mg 0 02 NbO 4 was prepared and studied. The phase content and the sample microstructure was examined by an X-ray diffraction method and scanning electron microscopy. EDS measurements were done both for composite samples and the diffusion couple. The electrical properties were studied by four terminal DC method. The hightemperature interaction between the two components of the composite has been observed. It has been suggested that lanthanum diffused into the perovskite phase and substituted for calcium whereas calcium and niobium formed the Ca 2 Nb 2 O 7 pyrochlore phase. At 1500℃ very large crystallites of the pyrochlore were observed. Regardless of strong interaction between the composite components, its total conductivity was weakly dependent on the sintering temperature. PACS

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“…Therefore, studies of the relation between the morphology of these materials and their electrical properties are very important. Chemical stability together with cost effective substrates and manufacturing processes [15] present opportunity for alternative cathode materials, for example iron doped calcium titanates CaTi 1-x Fe x O 3-δ (CTF). The electronic and protonic conductivity of calcium titanate is caused by defect introduced by iron doping.…”

Section: Introductionmentioning

confidence: 99%

“…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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Influence of Microstructure on the Electrical Properties of Iron‐Substituted Calcium Titanate Ceramics

Cited by 33 publications

References 45 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

Characterization of CaTi0.9Fe0.1O3/La0.98Mg0.02NbO4 composite

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

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