This thesis focuses on developing an appropriate cathode material throughnanotechnology as a key component for a promising alternative of renewable energygenerating systems, Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC).Aiming at a working cathode material for IT-SOFC, a recently reported capable oxideperovskite material has been synthesized through two different chemical methods.BaxSr1-xCoyFe1-yO3−δ (BSCF) with y =0.8 and x =0.2 was fabricated in nanocrystallineform by a novel chemical alloying approach, co-precipitation- as well as conventionalsol-gel method to produce oxide perovskites. The thermal properties, phase constituents,microstructure and elemental analysis of the samples were characterized by TG-DSC,XRD, SEM and EDS techniques respectively. Thermodynamic modeling has beenperformed using a KTH-developed software (Medusa) and Spark Plasma Sintering (SPS)has been used to obtain pellets of BSCF, preserving the nanostructure and generatingquite dense pellets for electrical conductivity measurements.The results show that the powders synthesized by solution co-precipitation have cubicperovskite-type structure with a high homogeneity and uniform distribution and meanparticle size of 50-90 nm range, while sol-gel powders are not easy to form a pure phaseand mostly the process ends up with large particle containing two or three phases.Finer resultant powder compared to sol-gel technique and earlier research works onBSCF has been achieved in this project using oxalate co-precipitation method. Topreserve nanoscaled features of BSCF powder which possess a significant increase ofelectrical conductivity due to decrease the electrical resistivity of grain boundaries, forthe sample synthesized through co-precipitation, ~92% dense pellet sintered by SPS atV1080 °C and under 50 MPa pressure and its electrical conductivity has been measuredfrom room temperature to 900 °C.Specific conductivity values were precisely measured and the maximum of 63 S.cm-1 at430 °C in air and 25 S.cm-1 at 375°C in N2 correspondingly are two times higher thanconventional BSCF implying a high pledge for nano-BSCF as a strong candidate ascathode material in IT-SOFC.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-159430 |
| Date | January 2009 |
| Creators | Darab, Mahdi |
| Publisher | KTH, Funktionella material, FNM, NTNU |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | KTH/ICT/MAP/FNM-2009-1 |
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