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Ferritic stainless steel (SS) interconnect used for intermediate temperature solid oxide fuel cell has issues associated with the growth of oxide scale on the surface and evaporation of chromium species to the cathode leading to increase in polarization resistance and hence, overall cell resistance. Protective coating is essentially applied over the SS surface to restrict the above phenomena. In the present investigation, strontium doped lanthanum manganese chromite (LSCM) of composition La 0 . 75 Sr 0 . 25 Cr 0 . 5 Mn 0.5 O 3 has been explored as a possible protective coating material on ferritic SS interconnect surface. For this application, fine LSCM powder was synthesized by solution polymerization method. Terpineol based slurry of LSCM was formulated and used for coating on ferritic SS surface by screen printing. LSCM coated ferritic SS was exposed to moist oxygen at 800 °C for 300 h and area specific resistance (ASR) of the coating was found to be as low as 2.0 mΩ cm 2 after exposure. Microstructure of LSCM coating and the chromium oxide film was investigated using SEM and EDS. The results indicate that LSCM can form an effective protective coating on ferritic stainless steel for SOFC interconnect application. [ABSTRACT FROM AUTHOR]

Abstract: Improvement of performances of SOFCs/SOECs demands the development of novel materials for its commercially viability and practicability in operations. For air electrode applications novel materials like cobalt based compounds, which offer both ionic and electronic conductivity (MIECs), to achieve high performance are very promising. Among these Pr1−xSrxFe1−yCoyO3−δ (PSCF) seems to be very suitable material for oxygen electrode in SOFCs. In the present study, we have chosen Pr0.58Sr0.4Fe0.8Co0.2O3−δ as the composition of the PSCF material. To overcome the high thermal expansion coefficient of this material with the electrolyte, 10mol% Gd doped ceria (GDC) is used as the composite material. Chemical compatibility between these two materials was ascertained by the XRD analysis of the calcined composite mixture. Composites of PSCF and GDC with different weight ratio were made and symmetric cells were fabricated using screen printing of the composite ink. Based on the polarisation resistance measurements, PSCF50–GDC50 composite was found to be suitable. From the dilatometric shrinkage curve of the composite pellet, a range of the possible sintering temperatures was identified. From the microstructural observations and the polarisation resistance measurement of the symmetric cells at 800°C under air, 1100°C was chosen as the most suitable sintering temperature. Optimization of the thickness of the screen printed electrode was carried out. From the symmetric cell measurements, the polarisation resistance of the electrodes having coating thickness from 8 to 9μm, has shown the minimum polarisation resistance of 0.12Ωcm² at 800°C in air atmosphere. Very low polarisation resistance of PSCF, suitable physical stability and microstructure indicates that this is a promising material for air electrode applications in improving the performance of SOFCs and SOECs. [Copyright &y& Elsevier]

Abstract: Ferroelectric strontium barium niobate (SBN) powder was synthesized by solid-state route. The green compacts were sintered in the temperature range 1250–1350°C in a microwave furnace. The microstructural study, using SEM, revealed the grain size in the range 2–20μm without microcracks, depending on the sintering temperature. This is in contrast to that obtained conventionally for sintered SBN powder synthesized by solid-state route, which resulted in duplex microstructure with microcracks [N.S. VanDamme, A.E. Sutherland, L. Jones, K. Bridger, S.R. Winzer, J. Am. Ceram. Soc. 74 (1991) 1785; P.K. Patro, A.R. Kulkarni, C.S. Harendranath, Ceram. Int. 30 (2004) 1405; P.K. Patro, Trans. Ind. Inst. Metals 59 (2006) 229]. Impedance analyzer and ferroelectric hysteresis loop tracer were used for the dielectric, ferroelectric, I–V and electric fatigue measurements. Microwave sintering also resulted in a dielectric maxima ε max 2590 at 1kHz (compared to 1103 for conventional sintering [P.K. Patro, A.R. Kulkarni, C.S. Harendranath, Ceram. Int. 30 (2004) 1405]) for the sintering temperature of 1350°C. Similar improvement in microwave-sintered SBN was observed depending on their sintering condition. The origin of this difference is attributed to microstructural differences arising from difference in heating method. In this paper the observed dielectric and ferroelectric behavior have been correlated with different sintering conditions and consequent microstructure due to microwave sintering. [Copyright &y& Elsevier]

Nano-sized Sr0.5Ba0.5Nb2O6 (SBN50) powder has been synthesized, at very short reaction time, for the first time by a novel combustion method. Ba(NO3)2 and Sr(NO3)2 were used as source of Sr and Ba, respectively, while Nb-oxalate was used as the source of niobium. Urea, hexamethyltetramine (HMT) and glycine were used as fuel. The crystallite sizes in the powder ranged between 14–125 nm. X-ray diffraction analysis showed complete SBN50 phase formation at 700 °C, when urea/HMT was used as fuel, and at 800 °C when glycine was used as fuel. Ferroelectric–paraelectric phase transition temperature (Tc) close to 40 °C was observed when urea and HMT were used and the Tc was −49 °C when glycine was used. When urea was used as fuel highest dielectric constant was observed for the pellets sintered at 1250 °C for 4 h. Low dielectric loss was observed when HMT was used as fuel. Larger grain sizes in the sintered pellets were observed when glycine was used as fuel. [Copyright &y& Elsevier]

We have performed magnetic and transport measurements on La[sub 0.67]Ca[sub 0.33]MnO[sub 3] polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its possible applications at room temperature. The microscopic studies in melt samples show an excellent connectivity between grains, suggesting the enhancement of percolative transport by opening new conduction channels and the disappearance of magnetic phase boundary at elevated temperature by the ordering of Mn spins blocked at the grain boundary of sintered samples. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Gadolinium cobaltite (GdCoO3) powder has been synthesized by solution polymerization method and characterized for its application as cathode material in gadolinia doped ceria (GDC) electrolyte based intermediate temperature SOFC (IT-SOFC). Perovskite structured phase pure and nanocrystalline GdCoO3 powder was obtained after calcining the precursor at 800°C. The powder was found to start sintering at about 850°C on heating and could be sintered to near theoretical density at 1200°C. The electrical conductivity of the sintered material was measured to be 580Scm−1 at 800°C and its coefficient of thermal expansion varied from 16×10−6 to 25×10−6 K−1 in the temperature range from 200 to 1000°C. GdCoO3–GDC (1:1wt.%) composite cathode was found to have coefficient of thermal expansion that match closely with GDC electrolyte. Symmetric cells were prepared using GDC electrolyte and GdCoO3–GDC composite as the electrode and the area specific resistance (ASR) for interfacial polarization was evaluated by AC impedance spectroscopic technique. ASR values of 1.1, 0.55 and 0.2Ωcm2 have been obtained at 800, 850 and 900°C, respectively. [Copyright &y& Elsevier]