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

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.

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

2012 ◽  
Vol 532-533 ◽  
pp. 35-39
Author(s):  
Jie Zhao ◽  
Ling Long Kong ◽  
Chen Li ◽  
Yong Chang Ma
Keyword(s):  
Cathode Materials ◽  
Oxygen Vacancies ◽  
Small Polaron ◽  
Negative Temperature ◽  
Intermediate Temperature ◽  
Charge Balance ◽  
Mixed Conductivity ◽  
Polaron Hopping ◽  
Lower Temperature ◽  
Perovskite Type

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.

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

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.

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

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.

Structural and electrical properties of Nd1.7Ba0.3Ni0.9Cr0.1O4+δ compound

2012 ◽  
Vol 27 (3) ◽  
pp. 184-188 ◽  
Author(s):  
Manel Jammali ◽  
Rached Ben Hassen ◽  
Jan Rohlicek
Keyword(s):  
Electrical Transport ◽  
Small Polaron ◽  
Sol Gel ◽  
Polycrystalline Sample ◽  
Xrd Analysis ◽  
Electrical Transport Properties ◽  
Polaron Hopping ◽  
X Ray ◽  
Cell Parameters ◽  
Structural And Electrical Properties

The Nd1.7Ba0.3Ni0.9Cr0.1O4+δ polycrystalline sample was synthesized by the sol–gel process and a subsequent annealing at 1523 K in 1 atm of flowing argon. X-ray diffraction (XRD) analysis and electrical transport properties have been investigated as well. The oxygen non-stoichiometry was determined by iodometric titration. The sample shows adoption of the K2NiF4-type structure based on a tolerance factor calculation. Rietveld refinement of the crystal structure from X-ray powder diffraction data confirmed that Nd1.7Ba0.3Ni0.9Cr0.1O4+δ adopts the tetragonal structure (space group I4/mmm, Z = 2). The room temperature unit-cell parameters are determined to be a = 3.82515(2) and c = 12.47528(6) Å. The reliability factors are: RB = 0.043, Rwp = 0.012 and χ2 = 3.00. The Nd1.7Ba0.3Ni0.9Cr0.1O4+δ compound exhibits a semi-conductive behaviour. The electrical transport mechanism has been investigated and it agrees with the adiabatic small polaron hopping model in the temperature range 313 K ≤ T ≤ 708 K.

Electrical transport properties of single-crystalline Mn–Zn ferrous ferrite

2001 ◽  
Vol 16 (3) ◽  
pp. 774-777 ◽  
Author(s):  
Yong-Chae Chung ◽  
Han-Ill Yoo
Keyword(s):  
Transport Properties ◽  
Thermoelectric Power ◽  
Electrical Transport ◽  
Small Polaron ◽  
Electrical Transport Properties ◽  
Polaron Hopping ◽  
Single Crystalline ◽  
Small Polaron Hopping ◽  
Hopping Model ◽  
Cation Redistribution

Electrical transport properties, electrical conductivity, and thermoelectric power of a single-crystalline Mn0.45Zn0.43Fe2.12O4 were measured as functions of temperature in the range of 25 to 1000 °C. According to the small polaron hopping model, the values of the activation energy for small polaron hopping (EH) were obtained from the conductivity data in three different temperature regions: 0.032 eV for T < TC, 0.12 eV for TC < T < 600 °C, and 0.25 eV for 600 °C < T < 1000 °C. The behavior of conductivity and thermoelectric power data above TC is discussed in connection with cation redistribution.

STUDY OF ELECTRICAL TRANSPORT AND AC SUSCEPTIBILITY IN LaMn1-xCuxO3

2005 ◽  
Vol 19 (06) ◽  
pp. 317-330 ◽  
Author(s):  
MANORANJAN KAR ◽  
S. RAVI
Keyword(s):  
Transition Temperature ◽  
Electrical Transport ◽  
Small Polaron ◽  
Ac Susceptibility ◽  
Ferromagnetic Transition ◽  
X Ray Diffraction ◽  
Polaron Hopping ◽  
Phase Form ◽  
Resistivity Data ◽  
Diffraction Patterns

LaMn 1-x Cu x O 3 compounds have been prepared in single phase form for x = 0 to 0.30. X-ray diffraction patterns recorded at room temperature could be mostly refined using Pbnm space group. Paramagnetic-to-ferromagnetic transitions have been observed up to x = 0.30, from ac susceptibility measurements. Metal–insulator transition in the vicinity of ferromagnetic transition temperature has been observed for x = 0.05 and the resistivity data in the metallic region could be explained in terms of electron–electron and electron–magnon scattering mechanisms. Further increase in Cu-doping beyond x = 0.05 leads to systematic decrease in ferromagnetic transition temperature and ultimately ferromagnetism is destroyed for x = 0.40. The resistivity data of all samples except x = 0.05 exhibit semiconducting behaviors and they could be mostly explained using the adiabatic small polaron hopping model.

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