Investigation on Preparation and Electrical Properties of Novel Perovskite Cathode Materials Doped with Multi-Elements for IT-SOFC

To develop novel cathode materials with high electrical performances for intermediate temperature solid oxide fuel cells (IT-SOFCs) and optimize the preparation process, perovskite-type oxides Pr1-x-ySrxCayCo1-zFezO3-δ (x=0.1, 0.2; y=0.1, 0.2; z=0.2, 0.3, 0.4; denoted as PSCCF-81182, PSCCF-72173 and PSCCF-62264) were prepared by solid state reaction. The formation process, phase structure and microstructure of the prepared samples were measured using TG-DTA, FT/IR, XRD and SEM techniques. The mixed conductivity of the samples was measured using DC four-terminal method in the range of 150-950 °C. Chemical state of the elements was measured by XPS experiments. The results show that the prepared samples PSCCF-81182, PSCCF-72173 and PSCCF-62264 exhibit a single phase with cubic perovskite structure after sintered at 1200 °C for 6 h. The mixed conductivity of the samples increases with temperature up to a maximum value, and then decreases. At lower temperature, the conductivity follows small polaron hopping mechanism. The negative temperature dependence occurring at higher temperature is due to the creation of oxygen vacancies for charge balance. At intermediate temperature (600-800 °C), the mixed conductivity values of the prepared samples are all much higher than 100 S•cm-1，and can meet the demand of cathode materials for IT-SOFC. XPS tests show that Co and Fe elements in PSCCF-72173 are all of + 3 and + 4 valence. Absorbed oxygen can also be found from the XPS patterns, which is related to the concentration of oxygen vacancies in the perovskite-type oxides.

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Synthesis and Electrical Transport Property of Sr and Cu-Doped LaFeO3-Based Cathode Material for IT-SOFC

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.710.33 ◽

2013 ◽

Vol 710 ◽

pp. 33-36

Author(s):

Jie Zhao ◽

Jiang Fu ◽

Yong Fu ◽

Yong Chang Ma

Keyword(s):

Cathode Material ◽

Electrical Transport ◽

High Performance ◽

Small Polaron ◽

Negative Temperature ◽

Rare Earth Oxide ◽

Intermediate Temperature ◽

Charge Balance ◽

Mixed Conductivity ◽

Polaron Hopping

In order to accelerate the commercialization of SOFCs technology, the key is the development of high performance cathode materials operated at intermediate temperature. Sr and Cu doped rare earth oxide La1-xSrxFe1-yCu.yO3-δ (x=0.1, 0.3 ; y=0.1, 0.2, denoted as LSFCu-11, LSFCu-31 and LSFCu-32 ) were synthesized by solid state reaction method (SSR). The formation process, phase structure and microstructure of the synthesized samples were characterized using TG/DSC, XRD and SEM. The thermal expansion coefficients (TEC) of the samples were analyzed by thermal dilatometry. The electrical conductivities of the samples were measured with DC four-terminal method from 25 to 950 °C. The results indicate that the samples exhibit a single phase with orthorhombic and hexagonal perovskite structure after sintered at 1200 °C for 4h. The electrical conductivity of the samples increases with temperature up to a maximum value, and then decreases gradually. The small polaron hopping is regarded as the conducting mechanism for synthesized samples at T 550 °C. The negative temperature dependence occurring at higher temperature is due to the creation of oxygen vacancies for charge balance. LSFCu-32 has higher mixed conductivity (> 100 S·cm-1) at intermediate temperature and can meet the demand of cathode material for IT-SOFC. In addition, the average TECs of LSFCu-11, LSFCu-31 and LSFCu-32 are 1.22 × 10-6 K-1 , 1.30 × 10-6 K-1 and 1.34 × 10-6 K-1 respectively.

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Characterization of Cathode Materials Ln0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85 (Ln=La, Pr and Nd) Synthesized by Microwave Sintering Techniques

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.771.59 ◽

2013 ◽

Vol 771 ◽

pp. 59-62

Author(s):

Jie Zhao ◽

Jiang Fu ◽

Yong Fu ◽

Yu Na Zhao ◽

Yong Chang Ma

Keyword(s):

Electrical Conductivity ◽

Cathode Materials ◽

Small Polaron ◽

Microwave Sintering ◽

X Ray Diffraction ◽

Mixed Conductivity ◽

Polaron Hopping ◽

Expansion Behavior ◽

Higher Temperature

Sr, Ca and Fe doped cathode materials Ln0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85 (LnSCCF, Ln=La, Pr and Nd; abbreviated as L-72173, P-72173 and N-72173) were synthesized by microwave sintering (MWS) techniques. The formation process, phase structure and composition were characterized using TG/DTA, XRD and EDS. The thermal expansion behavior of the samples was analyzed in the range of 20-950 °C by thermal dilatometer. The electrical conductivity of the samples was measured with DC four-terminal method from 25 to 900 °C. The X-ray diffraction shows that the samples exhibit a single phase with rhombohedral or cubic perovskite structure after sintered at 1200 °C for 20 min. The electrical conductivity of the samples increases with temperature up to a maximum, and then decreases gradually at higher temperature owing to the creation of oxygen vacancies. The small polaron hopping is regarded as the conducting mechanism (T 550 °C). L-72173 has higher mixed conductivity ( >300 S·cm-1) in 550-800 °C. The average TECs of L-72173, P-72173 and N-72173 are 1.389× 10-5 K-1, 1.417 × 10-5 K-1 and 1.416 × 10-5 K-1 in the range of 25-800 °C, respectively. They are thermally matched to the GDC better than the YSZ and SDC.

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Characterization of Novel Perovskite-Type La0.6Sr0.2Ca0.2Co1-YFeYO3-δ Cathode Materials Prepared by Solid State Reaction for IT-SOFCs

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.130-134.1058 ◽

2011 ◽

Vol 130-134 ◽

pp. 1058-1061

Author(s):

Chen Li ◽

Jie Zhao ◽

Ling Long Kong ◽

Yong Chang Ma

Keyword(s):

Thermal Expansion ◽

Solid State ◽

Cathode Materials ◽

Solid State Reaction ◽

Perovskite Phase ◽

Intermediate Temperature ◽

Mixed Conductivity ◽

Thermal Expansion Behavior ◽

Expansion Behavior ◽

Perovskite Type

Perovskite-type cathode materials La0.6Sr0.2Ca0.2Co1-yFeyO3-δ(0.2≤y≤0.5, marked as LSCCF62282, LSCCF62273, LSCCF62264 and LSCCF62255) for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were prepared by solid state reaction. The establishment process and phase transformation were measured by TG-DTA, FT/IR and XRD techniques. Single hexagonal perovskite phase can be achieved after sintered at 1100 °C for 3 h. Mixed conductivity, thermal expansion behavior and chemical stability of sintered samples at 1100 °C for 3 h have been investigated. At intermediate temperature (600-800 °C), the mixed conductivity characterized by DC four-probe technique is higher than 100 S/cm. LSCCF62282 has the highest conductivity of 297.3 S/cm at 700 °C among the four samples. At lower temperatures, the conductivity follows small polaron hopping mechanism. Thermal expansion coefficients (TECs) of the samples from 50 °C to 850 °C exhibit a reducing tendency with increasing amount of doped Fe3+. Thermal expansion behavior can be improved by doping with Ca2+and Fe3+commonly. XRD pattern for LSCCF62282 and YSZ mixture sintered at 800 °C for 6h indicates that cathode material LSCCF62282 is chemically stable against YSZ electrolyte at operating temperature.

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CRYSTAL STRUCTURE, ELECTRICAL CONDUCTIVITY AND THERMAL EXPANSION OF Pr1-xSrxFeO3-δ(0 ≤ x ≤ 0.6)

International Journal of Modern Physics B ◽

10.1142/s0217979212501743 ◽

2012 ◽

Vol 26 (32) ◽

pp. 1250174 ◽

Cited By ~ 1

Author(s):

V. PRASHANTH KUMAR ◽

Y. S. REDDY ◽

P. KISTAIAH ◽

C. VISHNUVARDHAN REDDY

Keyword(s):

Crystal Structure ◽

Electrical Conductivity ◽

Thermal Expansion ◽

Room Temperature ◽

Small Polaron ◽

Linear Thermal Expansion ◽

Lattice Parameter ◽

Polaron Hopping ◽

X Ray ◽

Perovskite Type

The crystal structure at room temperature (RT), thermal expansion from RT to 1000°C and electrical conductivity, from RT to 600°C, of the perovskite-type oxides in the system Pr 1-x Sr x FeO 3(x = 0, 0.2, 0.4, 0.6) were studied. All the compounds have the orthorhombic perovskite GdFeO 3-type structure with space group Pbnm. The lattice parameters were determined by X-ray powder diffraction. The Pseudo cubic lattice parameter decreases with an increase in x, while the coefficient of linear thermal expansion increases. The thermal expansion is almost linear for x = 0 and 0.2. The electrical conductivity increases with increasing x while the activation energy decreases. The electrical conductivity can be described by the small polaron hopping conductivity model.

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Synthesis and Characterization of the Cathode Materials La0.7Sr0.15Ca0.15Co1-yFeyO3-δ for ITSOFC

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.105-106.653 ◽

2010 ◽

Vol 105-106 ◽

pp. 653-656

Author(s):

W.Y. Gao ◽

Z.Q. Hu ◽

X.G. Sui ◽

C.M. Li ◽

N.L. Tang ◽

...

Keyword(s):

Electrical Conductivity ◽

Cathode Materials ◽

Raw Materials ◽

Small Polaron ◽

Polaron Hopping ◽

Metal Nitrates ◽

Conducting Mechanism ◽

A Site ◽

P Type

La0.7Sr0.15Ca0.15Co1-yFeyO3-δ(LSCCF)powders with 0.2y0.5 for the applications as the cathode materials in intermediate temperature solid oxide fuel cell(ITSOFC) were synthesized by glycine-nitrates-process(GNP) using metal-nitrates and glycine as the raw materials. The process, crystal structure and particles morphology of the powders calcined at 600°C,800°C,1000°C for 3h were characterized by IR,XRD and SEM. The experimental results show that co-doped Ca2+ and Sr2+ replacing some La3+ in A site and Fe3+ replacing some Co3+ in B site didn’t influence the formation of perovskite structure and the powders calcined at 800°C for 3h were high pure single perovskite state. The electrical conductivity of LSCCF samples sintered at 1200°C for 3h,was measured as a function of temperature from 100°C to 800°C by the four-probe DC method in air.As a result, the conducting mechanism of LSCCF is p-type small polaron hopping process, and the electrical conductivity are all higher than 100 S/cm. But the electrical conductivity of LSCCF samples increase with Fe3+ content decrease.

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Recent development on perovskite-type cathode materials based on SrCoO3 − δparent oxide for intermediate-temperature solid oxide fuel cells

Asia-Pacific Journal of Chemical Engineering ◽

10.1002/apj.2009 ◽

2016 ◽

Vol 11 (3) ◽

pp. 370-381 ◽

Cited By ~ 13

Author(s):

Mengran Li ◽

Wei Zhou ◽

Zhonghua Zhu

Keyword(s):

Fuel Cells ◽

Solid Oxide Fuel Cells ◽

Cathode Materials ◽

Solid Oxide ◽

Intermediate Temperature ◽

Oxide Fuel ◽

Perovskite Type

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ChemInform Abstract: Recent Development on Perovskite-type Cathode Materials Based on SrCoO3-δ. Parent Oxide for Intermediate-Temperature Solid Oxide Fuel Cells

ChemInform ◽

10.1002/chin.201648224 ◽

2016 ◽

Vol 47 (48) ◽

Author(s):

Mengran Li ◽

Wei Zhou ◽

Zhonghua Zhu

Keyword(s):

Fuel Cells ◽

Solid Oxide Fuel Cells ◽

Cathode Materials ◽

Solid Oxide ◽

Intermediate Temperature ◽

Oxide Fuel ◽

Perovskite Type

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Negative Thermal Sensitivity of La1-xSrxFeO3 Films Prepared by Screen-Printing Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.1617 ◽

2017 ◽

Vol 898 ◽

pp. 1617-1624

Author(s):

Xin De Zhu ◽

Yu Zhou ◽

Sheng Li Li

Keyword(s):

Activation Energy ◽

High Performance ◽

Screen Printing ◽

Small Polaron ◽

Thermal Sensitivity ◽

Negative Temperature ◽

Electric Transport ◽

Polaron Hopping ◽

Screen Printing Method ◽

Printing Method

The impacts of different Sr content on the phase structure, negative temperature coefficient (NTC) characteristic and conduction mechanism at high temperature of lanthanum strontium ferrite (La1-xSrxFeO3, x=0.1~0.6) (LSFO) films were systematically discussed. The LSFO films were prepared on the alumina substrate by the screen printing method. The results showed that the crystal structure transformed from orthorhombic (x=0.1~0.3) to rhombohedral (x=0.4~0.6). All the samples presented NTC performance. With increasing the Sr content, B values increased to the maximum 3885 K (x=0.4) and then decreased. Non-adiabatic small polaron hopping mechanism was dominant for their electric transport in the temperature range from 450 K to 873 K. The activation energy was calculated between 0.37 eV and 0.57 eV, and the sample La0.7Sr0.3FeO3 showed the minimum value of the activation energy. Therefore the La1-xSrxFeO3 (x=0.3, 0.4, 0.5) films have the potential to be developed into high-performance NTC resistors.

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Effect of Mn-Site for Al Substitution on Structural, Electrical and Magnetic Properties inLa0.67Sr0.33Mn1-xAlxO3Thin Films by Sol-Gel Method

Journal of Nanomaterials ◽

10.1155/2014/703072 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

H. Abdullah ◽

M. Syafiq Zulfakar ◽

S. Kien Chen

Keyword(s):

Small Polaron ◽

Sol Gel ◽

Theoretical Models ◽

Hysteresis Curve ◽

Polaron Hopping ◽

Gel Method ◽

Sol Gel Method ◽

Electrical And Magnetic Properties ◽

Average Grain Size ◽

Lower Temperature

NanocrystallineLa0.67Sr0.33Mn1-xAlxO3(x=0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) thin films have been prepared on quartz substrates by sol-gel method. The structural and morphology studies were investigated via X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). XRD graph patterns show rhombohedral distorted perovskite structures. FESEM images show that the average grain size decreased as the concentration ofxincreased. Electrical property was investigated using four-point probe technique. Resistivity results show that metal-insulator transition (MIT) temperatures (Tp) decreased when the concentration ofxincreased.Tpshifted to lower temperature when the concentration ofxincreased. The data was analyzed based on theoretical models, where the ferromagnetic resistivity is followed with the equationρ=ρo+ρ2T2, whereρois due to the significance of grain boundary effects and a second-term ~ρ2T2appears that might be applied to the electrons scattering. In the high temperature regime(T>Tp), the resistivity data can be well described by small polaron hopping (SPH) and variable range hopping (VRH) mechanisms. Magnetic property was investigated using a vibration sample magnetometer. All samples that were obtained showed hysteresis curve with the highest value of magnetization for samplex=0.10.

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