Nanograin Study of Polycrystalline Ceramics Based on Cerate-Zirconate via Two-Step Sintering Research Management Institute (Rmi) Universiti Teknologi Mara 40450 Shah Alam, Selangor Malaysia by : Azliana Ramli (original) (raw)
Related papers
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...
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.
Thermal expansion and lattice parameter of solid electrolyte based on cerate-zirconate ceramics
AIP Conference Proceedings, 2018
As a potential electrolyte for proton conducting solid oxide fuel cells, cerate-zirconate ceramics that belong to perovskite type-oxides are widely explored worldwide. This paper presents the thermal expansion of the electrolyte that becomes one of the crucial properties in the fuel cell fabrication. A sol gel method was used to prepare BaCe 0.54 Zr 0.36 Y 0.1 O 3-δ (BCZY) proton conductor with a combination of the high proton conductivity of barium cerate and good chemical stability of barium zirconate. After calcined at 1100°C for 10 h, the single-phase powder was pressed to become a pellet with 13 mm in diameter and 2 mm thickness. Scanning electron microscope (SEM) was done to observe the morphology of sample and lattice parameter was determined at room temperature using XRD. The thermal expansion of BCZY electrolyte has been investigated in air by using dilatometer in the temperature range of 30°C-1000°C at a heating rate of 10°C/min. The influence of thermal on the form of linear expansion of pellet BCZY as a function of temperature, ∆L/L˳ = f(T) which is ∆L is the length change and L˳ is the initial length has been plotted. The thermal expansion coefficient of BCZY is 8.53x10-6 /K with lattice parameter calculated is 4.344Å.
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.
World Journal of Nano Science and Engineering, 2011
The nano ceramic Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3 (BSCF) powders have been synthesized by Sol-Gel process using nitrate based chemicals for SOFC applications since these powders are considered to be more promising cathode materials for SOFC. Glycine was used as a chelant agent and ethylene glycol as a dispersant. The powders were calcined at 850˚C/3 hr in the air using Thermolyne 47,900 furnace. These powders were characterized by employing SEM/EDS, XRD and TGA/DTA techniques. The SEM images BSCF powder indicate the presence of highly porous spherical particles with nano sizes. The XRD results shows the formation of BSCF perovskite phase at the calcination temperature of 850˚C. From XRD line broadening technique, the average crystllite size of the BSCF powders were found to be around 9.15-11.83 nm and 13.63-17.47 nm for as prepared and after calcination at 850˚C respectively. The TGA plot shows that there is no weight loss after the temperature around 450˚C indicating completion of combustion.
Journal of Electrochemical Science and Technology, 2020
The article provides information on ceramic / nanostructured materials which are suitable for solid oxide fuel cells (SOFCs) working between 500 to 1000 o C. However, low temperature solid oxide fuel cells LTSOFCs working at less than 600 o C are being developed now-a-days with suitable new materials and are globally explored as the "future energy conversion devices". The LTSOFCs device has emerged as a novel technology especially for stationary power generation, portable and transportation applications. Operating SOFC at low temperature (i.e. < 600 o C) with higher efficiency is a bigger challenge for the scientific community since in low temperature regions, the efficiency might be less and the components might have exhibited lower catalytic activity which may result in poor cell performance. Employing new and novel nanoscale ceramic materials and composites may improve the SOFC performance at low temperature ranges is most focused now-a-days. This review article focuses on the overview of various ceramic and nanostructured materials and components applicable for SOFC devices reported by different researchers across the globe. More importance is given for the nanostructured materials and components developed for LTSOFC technology so far.
Materials Science and Engineering: B, 2019
In this study the oxygen deficient perovskite Ba 0.75 K 0.25 (Ca 0.5 Nb 0.5)O 2.75 (BKCN 25) is synthesized by solid state method via ball milling. Improvement in total conductivity through reducing grain boundary blocking effect is attempted by performing densification using conventional, microwave and spark plasma sintering. Physical characterizations of the pellets reveal structural stability and variation in morphology and porosity among the pellets sintered using different techniques. XRD analysis confirm cubic double perovskite structure in all sintered pellets but each having different grain sizes. SEM images show densified pellets with well-defined grains separated with grain boundary. AC impedance studies reveal that oxide ionic conductivity of BKCN 25 is ∼1.08 × 10 −3 S.cm −1 at 700°C in air atmosphere similar to reported GDC15, BaCe 0.5 Zr 0.3 Y 0.2 O 3-δ and BaCe 0.45 Zr 0.45 Sc 0.1 O 3-δ SOFC electrolytes. Significant enhancement in the total conductivity can be observed for spark plasma sintered BKCN 25 sample with lowest grain boundary blocking contribution.
Synthesis of Solid Oxide Fuel Cell Ceramic Materials from Aqueous Solutions
ECS Proceedings Volumes
Methods for synthesizing solid oxide fuel cell ceramic materials from aqueous solutions at ordinary temperatures and ordinary pressures are ad vantageous because of the applicability to making films with wide areas and/or complicated shapes with no requirement of vacuum or high tem perature, and because of lower cost. Solutions of fluoro-complex ions were obtained by dissolving sodium hexafluorozirconate in distilled water or dissolving LaMeO3 (Me=Cr, Mn, Fe, Co) or (La,Sr)MeO3 perovskite pre pared by usual solid state reaction in hydrofluoric acid. Boric acid was added into the solution, the fluoride ions were consumed by the formation of BF4' complex ion, and then the fluoro-complex ions were hydrolyzed to ZrO2, LaMeO3 or (La,Sr)MeO3 in order to increase the amount of fluoride ions. The high crystallinity of the product was confirmed by sharp and strong X-ray diffraction peaks. Aggregates of synthesized ZrO2, LaMeO3 or (La,Sr)MeO3 were observed on the substrates in scanning electron micro scope images. Deposition of LaMnO3 on yttria stabilized zirconia substrate was performed by using this method.