Preparation and Properties of Multi-Elements Doped Perovskite-Type Mixed Conductors for IT-SOFC Cathodes

2014 ◽  
Vol 989-994 ◽  
pp. 759-762
Author(s):  
Jiang Fu ◽  
Jie Zhao ◽  
Yong Fu ◽  
Rong Rong Li
Keyword(s):  
Perovskite Phase ◽  
Mixed Conductors ◽  
Forming Process ◽  
Mixed Conductivity ◽  
Conventional Solid State Reaction ◽  
Thermal Expansion Coefficients ◽  
Pure Perovskite Phase ◽  
Expansion Coefficients ◽  
Perovskite Type ◽  
Semiconducting Behavior

Multi-elements doped LaCoO3-based mixed conductors La0.7Sr0.1Ca0.1Co0.8Fe0.2O2.9 (LSCCF-112) and La0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85 (LSCCF-213) were synthesized by conventional solid state reaction (CSSR). The forming process, microstructure and crystal structure of the prepared samples were analyzed by TG/DTA, SEM and XRD. The mixed conductivities of the samples were measured using DC four-terminal method in 150-950 °C. Thermal expansion coefficients (TEC) of the samples were tested in 20-950°C. LSCCF-112 and LSCCF-213 exhibit pure perovskite phase and porous structure after sintered at 1200 °C. The average TECs of LSCCF-112 and LSCCF-213 are 18.17×10-6 K-1 and 17.52×10-6 K-1 respectively. The mixed conductivity of the samples shows semiconducting behavior up to 700-750°C and then decreases as the temperature is further raised. At intermediate temperature (IT), the conductivity values of the samples are both much higher than 100 S/cm.

Influence of Cr deficiency on sintering, thermal expansion and electrical properties of La0.75Sr0.25Cr1−xO3−δ as a SOFC interconnect material

2016 ◽  
Vol 30 (11) ◽  
pp. 1650127 ◽  
Author(s):  
Yi Ren ◽  
Wen Ma ◽  
Xiaoying Li ◽  
Jun Wang ◽  
Yu Bai ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Electrical Properties ◽  
Perovskite Phase ◽  
Ignition Process ◽  
Thermal Expansion Coefficients ◽  
Auto Ignition ◽  
Pure Perovskite Phase ◽  
Maximum Conductivity ◽  
Expansion Coefficients ◽  
Interconnect Material

The SOFC interconnect materials La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] [Formula: see text]–[Formula: see text] were prepared using an auto-ignition process. The influences of Cr deficiency on their sintering, thermal expansion and electrical properties were investigated. All the samples were pure perovskite phase after sintering at 1400[Formula: see text]C for 4 h. The cell volume of La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] decreased with increasing Cr deficient content. The relative density of the sintered bulk samples increased from 93.2% [Formula: see text] to a maximum value of 94.7% [Formula: see text] and then decreased to 87.7% [Formula: see text]. The thermal expansion coefficients of the sintered bulk samples were in the range of [Formula: see text]–[Formula: see text] (30–1000[Formula: see text]C), which are compatible with that of YSZ. Among the investigated samples, the sample with 0.02 Cr deficiency had a maximum conductivity of 40.4 Scm[Formula: see text] and the lowest Seebeck coefficient of 154.8 [Formula: see text]VK[Formula: see text] at 850[Formula: see text]C in pure He. The experimental results indicate that La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] has the best properties and is much suitable for SOFC interconnect material application.

Negative Thermal Expansion of Yb2Mo3O12 and Lu2Mo3O12

2008 ◽  
Vol 368-372 ◽  
pp. 1662-1664 ◽  
Author(s):  
X.L. Xiao ◽  
M.M. Wu ◽  
J. Peng ◽  
Y.Z. Cheng ◽  
Zhong Bo Hu
Keyword(s):  
Thermal Expansion ◽  
Solid State ◽  
Solid State Reaction ◽  
Linear Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Orthorhombic Structure ◽  
Conventional Solid State Reaction ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Compounds Yb2Mo3O12 and Lu2Mo3O12 were prepared by conventional solid-state reaction. Their crystal structures and thermal expansion properties were investigated. It was found that Yb2Mo3O12 and Lu2Mo3O12 adopt orthorhombic structure and show negative thermal expansion (NTE) in the temperature range of 200-800 °C. Their a-axis and c-axis exhibit stronger contraction in the temperature range of 200-800 °C, while b-axis slightly expands in the temperature range of 200-300 °C and then contracts in the temperature range of 300-800 °C. The linear thermal expansion coefficients al of Yb2Mo3O12 and Lu2Mo3O12 are −5.17 × 10−6 °C−1 and −5.67 × 10−6 °C−1, respectively.

Synthesis of Modified K0.5Na0.5NbO3 Powder by Molten-Salt Technique

2017 ◽  
Vol 728 ◽  
pp. 160-165
Author(s):  
Thanatep Phatungthane ◽  
Buagun Samran ◽  
Gobwute Rujijanagul
Keyword(s):  
Molten Salt ◽  
Calcination Temperature ◽  
Perovskite Phase ◽  
Orthorhombic Symmetry ◽  
Molten Salt Method ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Fine Grain ◽  
Pure Perovskite Phase

In the present work, the molten-salt method was applied to synthesize 0.948K0.5Na0.5NbO3–0.052LiSbO3 powder for the first time. Characteristics of the powder were investigated. Based on X-ray diffraction technique, pure perovskite phase was observed at a calcination temperature of 700 oC which is lower than that required by the conventional solid-state reaction technique for ∼200 oC. Raman spectroscopy technique showed that the powder had an orthorhombic symmetry which consistent with the X-ray diffraction results. The powder exhibited very fine grain with narrow size distribution. Particle size of the obtained powders increased with increasing calcination temperature. Therefore, the molten-salt method is a simple and effective method to synthesize 0.948K0.5Na0.5NbO3 – 0.052LiSbO3 powder.

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

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.

scholarly journals Structural, Dielectric and Ferroelectric Properties of Cu2+ and Cu2+/Bi3+ doped BCZT Lead-free Ceramics: A Comparative Study

2021 ◽  
Author(s):  
Sapna Kumari ◽  
Amit Kumar ◽  
V. Kumar ◽  
S. K. Dubey ◽  
P. K. Goyal ◽  
...  
Keyword(s):  
Perovskite Phase ◽  
Ferroelectric Properties ◽  
Solid State Reaction Method ◽  
Lead Free ◽  
X Ray Diffraction ◽  
Physical Mechanisms ◽  
A Value ◽  
Lead Free Ceramics ◽  
Pure Perovskite Phase ◽  
Perovskite Type

Abstract Perovskite type Ba0.98Ca0.02Zr0.02Ti0.98O3 (BCZT), Ba0.98Ca0.02Zr0.02Ti0.976Cu0.008O3 (BCZTC) and Ba0.9725Bi0.005Ca0.02Zr0.02Ti0.976Cu0.008O3 (BCZTCB) lead-free ceramics were synthesised via solid-state reaction method at a sintering temperature of ~ 1380°C. Effects of CuO and Bi2O3/CuO doping on structural, microstructural, dielectric, and ferroelectric properties were investigated systematically. X-ray diffraction technique confirmed the existence of pure perovskite phase with the tetragonal structure in pure and in the doped BCZT ceramics at room temperature. The dielectric analysis demonstrated two anomalies around 24°C and 126°C for BCZT, which were identified as orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC) phase transition temperature, respectively. The TO-T temperature shifted to below 16°C, while the TC increased to 132°C for the BCZTCB sample. The physical mechanisms of the conduction processes were investigated through impedance spectroscopy and the values of resistance, conductivity, and activation energies associated with the grain and grain boundaries were evaluated. The activation energy was determined to be higher for doped samples than for pure BCZT. Further, the dopant-dependent ferroelectric nature of the ceramic samples was evidenced by the analysis of characteristic hysteresis loop, and a value of remnant polarisation (Pr = 4.59 µC/cm2) was obtained for the BCZTCB ceramic sample. Furthermore, the d33 value, which was 54 pC/N for pure BCZT, was determined to be 140 pC/N and 64 pC/N for BCZTC and BCZTCB, respectively.

scholarly journals Influence of Ti addition on thermophyscial properties of Sm2Ce2O7 oxides

2018 ◽  
Vol 12 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Xiaoge Chen ◽  
Hongsong Zhang ◽  
Longfei Zhou ◽  
Bo Ren ◽  
An Tang ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Phonon Scattering ◽  
Solid State Reaction Method ◽  
Cold Isostatic Pressing ◽  
Conventional Solid State Reaction ◽  
Single Defect ◽  
Thermal Expansion Coefficients ◽  
Fluorite Type ◽  
Ion Radius ◽  
Expansion Coefficients

Sm2(Ce1-xTix)2O7 (where x = 0, 0.1,0.3, 0.5) solid solutions were synthesized by conventional solid state reaction method using Sm2O3, CeO2 and TiO2 as raw reactants. The synthesized powders were pressed into pellets by cold isostatic pressing and pressure-less sintered at 1600 ?C for ten hours. Their phase-structure and thermophysical properties were studied. The synthesized samples exhibit single defect fluorite-type structure. Due to the phonon scattering by substitutional atoms, the thermal conductivities of the Sm2(Ce1-xTix)2O7 solid solutions decrease with the increasing Ti4+ content over the entire temperature range, which are significantly lower than that of yttrium stabilized zirconia (YSZ). The thermal expansion coefficients of the prepared Sm2(Ce1-xTix)2O7 solid solutions also decrease with the increasing Ti4+ fraction, which can be attributed to the lower titanium ion radius.

Defects in β-SiC thin films grown on α-SiC substrates

1988 ◽  
Vol 46 ◽  
pp. 568-569
Author(s):  
Karren L. More
Keyword(s):  
Thin Films ◽  
Semiconductor Device ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Substrate Material ◽  
Growth Interface ◽  
Si Substrates ◽  
Thermal Expansion Coefficients ◽  
Device Applications ◽  
Expansion Coefficients

Beta-SiC is an ideal candidate material for use in semiconductor device applications. Currently, monocrystalline β-SiC thin films are epitaxially grown on {100} Si substrates by chemical vapor deposition (CVD). These films, however, contain a high density of defects such as stacking faults, microtwins, and antiphase boundaries (APBs) as a result of the 20% lattice mismatch across the growth interface and an 8% difference in thermal expansion coefficients between Si and SiC. An ideal substrate material for the growth of β-SiC is α-SiC. Unfortunately, high purity, bulk α-SiC single crystals are very difficult to grow. The major source of SiC suitable for use as a substrate material is the random growth of {0001} 6H α-SiC crystals in an Acheson furnace used to make SiC grit for abrasive applications. To prepare clean, atomically smooth surfaces, the substrates are oxidized at 1473 K in flowing 02 for 1.5 h which removes ∽50 nm of the as-grown surface. The natural {0001} surface can terminate as either a Si (0001) layer or as a C (0001) layer.

Influence of Magnetoelastic Anisotropy on Properties of Nanostructured Microwires

2013 ◽  
Vol 646 ◽  
pp. 59-66 ◽  
Author(s):  
Arcady Zhukov ◽  
Margarita Churyukanova ◽  
Lorena Gonzalez-Legarreta ◽  
Ahmed Talaat ◽  
Valentina Zhukova ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Hysteresis Loops ◽  
Magnetic Behaviour ◽  
Soft Magnetic ◽  
Magnetoelastic Anisotropy ◽  
Thermal Expansion Coefficients ◽  
Magnetoelastic Energy ◽  
Expansion Coefficients ◽  
The Difference ◽  
Magneto Resistance

We studied the effect ofthe magnetoelastic ansitropy on properties of nanostructured glass-coated microwires with soft magnetic behaviour (Finemet-type microwires of Fe70.8Cu1Nb3.1Si14.5B10.6, Fe71.8Cu1Nb3.1Si15B9.1 and Fe73.8Cu1Nb3.1Si13B9.1 compositions) and with granular structure (Cu based Co-Cu microwires). The magnetoelastic energy originated from the difference in thermal expansion coefficients of the glass and metallic alloy during the microwires fabrication, affected the hysteresis loops, coercivity and heat capacity of Finemet-type microwires. Hysteresis loops of all as-prepared microwires showed rectangular shape, typical for Fe-rich microwires. As expected, coercivity, HC, of as-prepared microwires increases with decreasing of the ratio ρ defined as the ratio between the metallic nucleus diameter, d to total microwire diameter, D. On the other hand we observed change of heat capacity in microwires with different ratio ρ. In the case of Co-Cu microwires ρ- ratio affected the structure and the giant magneto-resistance of obtained microwires.

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