Atanu Dutta

Alanine Assisted Low-Temperature Synthesis and Characterization of Nanocrystalline SOFC Cathodes

Nanocrystalline SOFC cathode materials of perovskite family, La(1-x)Sr(x)M(1-y)Co(y)O(3), where 0<x <= 0.5, 0<y <= 0.8 (M is transitional metal=Mn or Fe) have been synthesized at a relatively low temperature by combustion technique using alanine as novel fuel. The thermal analyses of the precursor gels show sharp single step combustion with low decomposition temperature (170-200 degrees C). Detailed X-ray powder diffraction analyses show 47-96% phase purity in the assynthesized powder and upon calcination at temperature similar to 825 degrees C, single phase material is obtained wherein the nanocrystallinity (crystallite size similar to 19-24 nm) is retained. Densification studies of the materials are carried out within 900-1100 degrees C. The coefficient of thermal expansion (CTE) of the sintered cathodes is also measured. Detailed electrical characterizations of the sintered cathodes are evaluated and correlated with the microstructures. The electrochemical performances of SOFC single cells (Ni-YSZ anode-support /YSZ similar to 20 mu m/LaFeO(3)-based cathodes) with ceria interlayer show high current density of similar to 1.2 A/cm(2) at 0.7 V at 800 degrees C.

Development of Anode-supported Planar SOFC using Inexpensive and Simple Processing Technique

In the anode-supported planar SOFC, conventionally the porous anode support is fabricated first, over which a thin layer of electrolyte (5-50 mu m) is developed to form the half-cell. Additionally, functional layers in the anode side (AFL) and cathode side (CFL) are used. The present contribution reports use of inexpensive and simple processing techniques to fabricate anode-supported planar SOFC where no AFL is used. The process involves room temperature lamination of several layers of tapecast NiO-YSZ together with a top layer of YSZ followed by co-firing. The half cells thus fabricated, having thin electrolyte (similar to 20 mu m), are screen-printed with La(Sr)MnO(3) (LSM)-YSZ CFL and LSM cathode layer. Single cells of dimensions up to 10 cm x 10 cm x 1.5 mm have been fabricated. Coupon cells show current density between 1.0 and 1.5 A/cm(2) at 800 degrees C and 0.7V. The electrochemical performances of these cells are size independent and show excellent repeatability.

Ionic conductivity studies on neodymium doped ceria in different atmospheres

Nano-crystalline 10 and 20 mol% neodymium (Nd) doped ceria powders were prepared by gel-combustion synthesis. The single-phase nature of the nano powder has been confirmed by X-ray diffraction. These sinter-active nano powders resulted in dense products, as the sintered densities were found to be ∼90% of theoretical densities. Ionic conductivity studies were carried out in air, hydrogen and oxygen atmospheres. The samples showed ionic conductivity of 1.3 × 10−2 S cm−1 at 650°C, and the activation energy values obtained in this system were in the range of 0.7-1.0 eV. These studies also revealed that no electronic conduction was observed, as the ionic conductivity values were almost similar in different environments.

Combustion Synthesis of La0.6Sr0.4Co0.98Ni0.02O3 Cathode and Evaluation of its Electrical and Electrochemical Properties for IT-SOFC

Nanocrystalline powder (30-40 nm) of 2 mol% Ni-doped lanthanum strontium cobaltite (La0.6Sr0.4Co0.98Ni0.02O3) was synthesized by combustion technique using glycine as fuel with various combinations of fuel to nitrate ratios. The thermal analysis revealed that the crystallization process is not single step and remained incomplete even up to 700{degree sign}C. In XRD analysis, existence of two minor phases was observed in addition to lanthanum strontium cobaltite phase. One particular synthesis condition i.e., with a slightly fuel excess ratio (0.45) showed highest electrical conductivity of 96 S/cm at 800{degree sign}C in air. For the application as cathode in SOFC, this material was studied in the symmetric cell mode with Gd-doped CeO2 as electrolyte and it showed lowest interfacial polarization resistance of 0.158 •cm2 when sintered at 1000{degree sign}C. Significantly high current density of ~ 3.4 A/cm2 and power density of ~ 2.4 W/cm2 at 800{degree sign}C was obtained with this cathode in anode-supported single cell with doped CeO2 as a buffer layer.