Strontium Dopant Concentrations Influence on Nd1-xSrxMnO3±δ Structural and Electrical Conductivity

2010 ◽  
Vol 660-661 ◽  
pp. 636-640
Author(s):  
Reinaldo Azevedo Vargas ◽  
Rubens Chiba ◽  
Marco Andreoli ◽  
Emília Satoshi Miyamaru Seo
Keyword(s):  
Electrical Conductivity ◽  
Perovskite Structure ◽  
Small Polaron ◽  
Ceramic Materials ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
X Ray Diffraction ◽  
Polaron Hopping ◽  
Different Types ◽  
Fuel Cell Cathode

Many different types of ceramic materials are currently being studied as possible cathodes in Solid Oxide Fuel Cells (SOFC), in an attempt to reduce operating temperatures. Strontium-doped neodymium manganite (Nd1-xSrxMnO3±δ) was used as an intermediate temperature solid oxide fuel cell cathode. X-ray diffraction and electrical conductivity of the Nd1-xSrxMnO3±δ system with a perovskite structure were studied in function of x equal to 0.10, 0.30 and 0.50. An orthorhombic pseudo-perovskite structure was assigned to all powder compositions prepared by standard ceramic technique. Electrical conductivity was described by the small polaron hopping conductivity model, as well as, increases due to regular increments of Sr content for all compositions. Electrical conductivity was measured at 25.2, 26.4 and 37.1Scm-1 for x = 0.10, 0.30 and 0.50, respectively at 800°C.

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.

scholarly journals Suitability of Sm3+-Substituted SrTiO3 as Anode Materials for Solid Oxide Fuel Cells: A Correlation between Structural and Electrical Properties

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4042 ◽  
Author(s):  
Saurabh Singh ◽  
Raghvendra Pandey ◽  
Sabrina Presto ◽  
Maria Paola Carpanese ◽  
Antonio Barbucci ◽  
...  
Keyword(s):  
Oxygen Content ◽  
Conduction Mechanism ◽  
Small Polaron ◽  
Solubility Limit ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Solid Solubility Limit ◽  
Polaron Hopping ◽  
Auto Combustion ◽  
Lower Oxygen

Perovskite anodes, nowadays, are used in any solid oxide fuel cell (SOFC) instead of conventional nickel/yttria-stabilized zirconia (Ni/YSZ) anodes due to their better redox and electrochemical stability. A few compositions of samarium-substituted strontium titanate perovskite, SmxSr1−xTiO3−δ (x = 0.00, 0.05, 0.10, 0.15, and 0.20), were synthesized via the citrate-nitrate auto-combustion route. The XRD patterns of these compositions confirm that the solid solubility limit of Sm in SrTiO3 is x < 0.15. The X-ray Rietveld refinement for all samples indicated the perovskite cubic structure with a P m 3 ¯ m space group at room temperature. The EDX mapping of the field emission scanning electron microscope (FESEM) micrographs of all compositions depicted a lower oxygen content in the specimens respect to the nominal value. This lower oxygen content in the samples were also confirmed via XPS study. The grain sizes of SmxSr1−xTiO3 samples were found to increase up to x = 0.10 and it decreases for the composition with x > 0.10. The AC conductivity spectra were fitted by Jonscher’s power law in the temperature range of 500–700 °C and scaled with the help of the Ghosh and Summerfield scaling model taking νH and σdc T as the scaling parameters. The scaling behaviour of the samples showed that the conduction mechanism depends on temperature at higher frequencies. Further, a study of the conduction mechanism unveiled that small polaron hopping occurred with the formation of electrons. The electrical conductivity, in the H2 atmosphere, of the Sm0.10Sr0.90TiO3 sample was found to be 2.7 × 10−1 S∙cm−1 at 650 °C, which is the highest among the other compositions. Hence, the composition Sm0.10Sr0.90TiO3 can be considered as a promising material for the application as the anode in SOFCs.

scholarly journals DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

2017 ◽  
Vol 35 (1) ◽  
pp. 40-44 ◽  
Author(s):  
W. Madhuri ◽  
S. Roopas Kiran ◽  
M. Penchal Reddy ◽  
N. Ramamanohar Reddy ◽  
K.V. Siva Kumar
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Small Polaron ◽  
X Ray Diffraction ◽  
High Definition ◽  
Conventional Solid State Reaction ◽  
Polaron Hopping ◽  
Dc Electrical Conductivity ◽  
Phase Spinel ◽  
Diffraction Patterns

AbstractNonstoichiometric series of Mg0.5−xCuxZn0.5Fe1.9O4−δ where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD). The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 °C and 400 °C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient α decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.

Sign in / Sign up

Export Citation Format

Share Document