Azad_Synthesis,-chemical-stability-and-proton-conductivity-of-the-perovksites-Ba(Ce,Zr)1-x-Scx-O3---δ_2007.pdf (original) (raw)
Related papers
Fuel Cells, 2008
Proton conducting perovskite oxides have been widely investigated because of their potential as electrolytes for intermediate temperature solid oxide fuel cells. Among them, BaCeO3- based materials exhibit good proton conductivity under a humidified hydrogen-containing atmosphere, but rather poor chemical stability in CO2 atmosphere. The substitution with Zr for Ce improves the chemical stability but reduces proton conductivity due to difficulties in fabricating dense materials. In the present work, single phase nanostructured powders of Ba1+xCe0.65Zr0.20Y0.15O3–δ (x = 0, 0.05, 0.10) solid solutions have been prepared by a modified sol–gel Pechini method with the final aim of evaluating the role of barium on their chemical and electrical properties. A significant influence of barium excess on the preparation and on properties of these materials has been demonstrated. In fact, density measurements evidenced that a 5 or 10 mol% nominal barium excess sensibly favoured the sintering process. Impedance analyses of sintered pellets confirmed the necessity of barium excess in order to avoid the lowering of proton conductivity, which has been evidenced for samples having stoichiometric barium content. Moreover, an unforeseen increase in chemical stability in CO2-containing atmosphere with the growth of the barium excess was detected by thermogravimetric analyses.
Solid State Ionics, 2017
Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ (BSCZGY) proton conducting electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been synthesized by a sol-gel modified Pechini process and its sinterability, thermal expansion, microstructure, ionic conductivity and chemical stability have been investigated. Ionic conductivity at 700 ºC was measured to be ~ 8 x 10-3 S cm-1 in wet 5 vol% H2/Ar atmospheres. Chemical stability test in pure CO2 up to 1200 ºC shows that the material is highly stable; better than the stability of BaZr0.3Ce0.5Y0.1Yb0.1O3-δ.
Sustainability
Perovskite materials have gained a lot of interest in solid oxide fuel cell (SOFC) applications owing to their exceptional properties; however, ideal perovskites exhibit proton conduction due to availability of low oxygen vacancies, which limit their application as SOFC electrolytes. In the current project, Sm was doped at the B-site of a BaCe0.7-xSmxZr0.2Y0.1O3-δ perovskite electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolytes were synthesized through a cost-effective coprecipitation method and were sintered at a low sintering temperature. The effects of samarium (Sm) doping on the electrochemical performance of BaCe0.7-xSmxZr0.2Y0.1O3-δ were investigated. X-ray diffraction (XRD) analysis confirmed that the BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolyte material retained the perovskite structure. The secondary phase of Sm2O3 was observed for BaCe0.4Sm0.3Zr0.2Y0.1O3-δ. Scanning electron microscopic (SEM) imaging displayed the dense...
Journal of The Electrochemical Society, 2010
The chemical stability and electrical properties of three promising perovskite-related structures BaCe 0.8 Gd 0.15 Pr 0.05 O 3−␦ , BaCe 0.85 Sm 0.15 O 3−␦ , and BaCe 0.85 Eu 0.15 O 3−␦ were tested in air, humidified N 2 and H 2 , as well as in D 2 O + N 2. Powder X-ray diffraction studies confirmed the formation of a cubic perovskite-like structure. The change in the lattice constant was consistent with B-site substitution in BaCeO 3. All the investigated compounds formed barium carbonate in CO 2 at elevated temperatures and were found to be chemically unstable in boiling H 2 O. The data showed that these three compounds are chemically stable in humidified CH 4 at 800°C; however, at 600°C, the formation of barium carbonate was observed. The electrical conductivity in wet N 2 and/or H 2 was found to be higher than that in the D 2 O-containing atmosphere, confirming proton conduction in the doped BaCeO 3. The Gd + Pr co-doped BaCeO 3 showed the highest total conductivity of 2.58 ϫ 10 −2 S cm −1 in H 2 + 3% H 2 O at 700°C with an activation energy of 0.36 eV in the temperature range of 450-700°C.
Chemically stable proton conducting doped BaCeO₃ -no more fear to SOFC wastes
Scientific reports, 2013
Development of chemically stable proton conductors for solid oxide fuel cells (SOFCs) will solve several issues, including cost associated with expensive inter-connectors, and long-term durability. Best known Y-doped BaCeO3 (YBC) proton conductors-based SOFCs suffer from chemical stability under SOFC by-products including CO2 and H2O. Here, for the first time, we report novel perovskite-type Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ by substituting Sr for Ba and co-substituting Gd + Zr for Ce in YBC that showed excellent chemical stability under SOFC by-products (e.g., CO2 and H2O) and retained a high proton conductivity, key properties which were lacking since the discovery of YBCs. In situ and ex- situ powder X-ray diffraction and thermo-gravimetric analysis demonstrate superior structural stability of investigated perovskite under SOFC by-products. The electrical measurements reveal pure proton conductivity, as confirmed by an open circuit potential of 1.15 V for H2-air cell at 700°C, an...
Scientific Reports
In this study, the Ho-substituted BaZrO 3 electrolyte ceramics (BaZr 1-x Ho x o 3-δ , 0.05 ≤ x ≤ 0.20) were synthesized through a low-cost flash pyrolysis process followed by conventional sintering. The effects of Ho-substitution in BaZrO 3 studied in terms of the structural phase relationship, microstructure and electrical conductivity to substantiate augmented total electrical conductivity for intermediate temperature solid oxide fuel cells (IT-SOFCs). The Rietveld refined X-ray diffraction (XRD) patterns revealed that pure phase with Pm m 3 space group symmetry of cubic crystal system as originated in all samples sintered at 1600 °C for 8 h. The Raman spectroscopic investigations also approved that Ho incorporation in BaZro 3 ceramics. Field Emission Scanning Microscopic (FESEM) study informed a mixture of fine and coarse grains in the fracture surface of Ho-substituted BaZrO 3 sintered samples. The relative density and average grain size of samples were observed to decrease as per the addition of Hosubstitution in BaZro 3 ceramics. The electrical conductivity study was accomplished by Electrical Impedance Spectroscopy (EIS) under 3% humidified O 2 atmosphere from 300 to 800 °C. Furthermore, the total electrical conductivity of BaZr 0.8 Ho 0.2 o 3-δ ceramic was found to be 5.8 × 10 −3 S-cm −1 at 600 °C under 3% humidified atmosphere, which may be a promising electrolyte for IT-SOFCs. Recently, the proton conductive oxide ceramics have fascinated worldwide attention due to widespread applications in intermediate temperature solid oxide fuel cells (IT-SOFCs), hydrogen separation and electrolysis of steam, etc. In this context, the rare-earth cerates and zirconates with the perovskite-type A(II)B(IV)O 3 crystallographic structure are the two foremost families of proton-conducting oxides for electrochemical applications 1-4. Generally, in these categories of oxide materials, oxygen vacancies are increased by replacement of tetravalent cation B(IV) by trivalent cation M(III) as given in the Eq. (1) using Kröger-Vink notation.
Processing and Application of Ceramics, 2018
The new compositions of BaCe 0.5 Zr 0.3 Y 0.15-x Yb x Zn 0.05 O 3-δ perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500°C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500°C. The protonic conductivities at 650°C were 2.8×10-4 S/cm and 4.2×10-3 S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system.
Journal of Alloys and Compounds, 2019
In present work, perovskite structured proton conducting electrolyte materials BaZr 0.8 Y 0.2 (BZY), BaZr 0.8 Gd 0.2 (BZGd) and BaZr 0.8 Sm 0.2 (BZSm) synthesized by cost effective combustion method are investigated for intermediate temperature solid oxide fuel cell (IT-SOFC). The synthesized BZY, BZGd and BZSm materials are sintered at low temperature (1150 C) and the effect of low sintering temperature on electrolyte properties are also explored. Microstructure, surface morphology, elemental composition, functional group and weight loss are studied using different characterization techniques like XRD, SEM, EDX, FTIR and TGA. XRD shows cubic perovskite structure of all synthesized materials. Secondary phase of Y 2 O 3 is observed in BZY while BaO is observed in BZGd and BZSm due to low sintering temperature. SEM micrographs reveals dense microstructure of BZSm compared to BZY and BZGd. EDX analysis confirms the required material composition within all samples with no impurities. FTIR shows the presence of hydroxyl group and metal oxides and it is observed that BZY exhibit more structural symmetry compared to BZSm and BZGd. Highest conductivity observed ð2:2 Â10 À3 S=cmÞ for BZY due to its structural symmetry and characteristic to prefer B-site of perovskite. Also significant power densities of 0.34 Wcm À2 , 0.24 Wcm À2 and 0.32 Wcm À2 for BZY, BZGd and BZSm electrolytes based cells at 650 C implies that BZY, BZGd and BZSm can be used as IT-SOFC electrolytes.
Inorganic Chemistry, 2011
We report the effect of donor-doped perovskitetype BaCeO 3 on the chemical stability in CO 2 and boiling H 2 O and electrical transport properties in various gas atmospheres that include ambient air, N 2 , H 2 , and wet and dry H 2 . Formation of perovskite-like BaCe 1Àx Nb x O 3(δ and BaCe 0.9Àx Zr x Nb 0.1 O 3(δ (x = 0.1; 0.2) was confirmed using powder X-ray diffraction (XRD) and electron diffraction (ED). The lattice constant was found to decrease with increasing Nb in BaCe 1Àx Nb x O 3(δ , which is consistent with Shannon's ionic radius trend. Like BaCeO 3 , BaCe 1Àx Nb x O 3(δ was found to be chemically unstable in 50% CO 2 at 700°C, while Zr doping for Ce improves the structural stability of BaCe 1Àx Nb x O 3(δ . AC impedance spectroscopy was used to estimate electrical conductivity, and it was found to vary with the atmospheric conditions and showed mixed ionic and electronic conduction in H 2 -containing atmosphere. Arrhenius-like behavior was observed for BaCe 0.9Àx Zr x Nb 0.1 O 3(δ at 400À700°C, while Zr-free BaCe 1Àx Nb x O 3(δ exhibits non-Arrhenius behavior at the same temperature range. Among the perovskite-type oxides investigated in the present work, BaCe 0.8 Zr 0.1 Nb 0.1 O 3(δ showed the highest bulk electrical conductivity of 1.3 Â 10 À3 S cm À1 in wet H 2 at 500°C, which is comparable to CO 2 and H 2 O unstable high-temperature Y-doped BaCeO 3 proton conductors.