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The La0.5Sr0.5Fe0.9Mo0.1O3 − δ-x wt.% SDC (LSFMo-xSDC, x = 0, 20, and 30) samples were evaluated as potential cathodes for solid oxide fuel cells (SOFCs) based on both La0.9Sr0.1Ga0.8Mg0.2O3 − δ (LSGM) and Sm0.2Ce0.8O2 − δ (SDC) electrolytes. The LSFMo cathode is chemically compatible with the LSGM and SDC electrolytes with temperature up to 1000 °C. Through the comparison of the polarization resistances (Rp) of the LSFMo cathode on LSGM and SDC electrolytes, only a small difference of ~ 13-15% in the Rp was obtained. To further improve the electrochemical performance of the LSFMo cathode, 20 and 30 wt.% SDC were introduced into the LSFMo cathode. The LSGM/SDC-supported single cell with LSFMo-20SDC composite cathode was found to show the optimal performance and excellent power cycle and long-time stability. In addition, the electrical conductivity and thermal expansion coefficient (TEC) for the LSFMo-20SDC cathode were also detected and evaluated. Our results show that the LSFMo-20SDC is a very promising candidate for use in the cathode of SOFC. [ABSTRACT FROM AUTHOR]

The 0.1 mol% Er3+ and 0-2 mol% Yb3+ codoped Al2O3 powders were prepared by the sol-gel method, and the phase structure, including only two crystalline types of doped Al2O3 phase, γ-(Al,Er,Yb)2O3 and θ-(Al,Er,Yb)2O3, was detected at the sintering temperature of 100°C. The visible and near infrared emissions properties depended strongly on the Yb3+ codoping, and the corresponding maximal peak intensities centered at about 523, 545, 660 and 1533 nm were obtained respectively for the 0.1 mol% Er3+ and 0.5 mol% Yb3+ codoped Al2O3 powders, which were composed of θ-(Al,Er,Yb)2O3 and a small amount of γ-(Al,Er,Yb)2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions, and the one-photon absorption process was involved in the near infrared emissions of the Er3+-Yb3+ codoped Al2O3 powders. [ABSTRACT FROM AUTHOR]

Perovskite oxides La x Sr 1–x Co 0.9 Sb 0.1 O 3– δ (LSCSbx, x=0.0–0.8) are investigated as IT–SOFC cathodes supported with La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ (LSGM) electrolyte. All LSCSbx oxides have a tetragonal distorted perovskite structure with s.g. P4/mmm , while a La 2 Co 2 O 5 impurity phase was observed within La doping levels at x=0.6–0.8. The LSCSb0.4 has a good chemical compatibility with LSGM electrolyte for temperatures up to 1050 °C. XPS examinations indicate the existence of Co 3+ /Co 4+ mixed valence states in LSCSbx. The conductivity increases with La doping and the LSCSbx with x=0.4 exhibits the highest electrical conductivity (e.g., 673–1637 S cm −1 at 300–850 °C). The thermal expansion coefficient (TEC) decreases from 25.89×10 –6 K –1 for x=0.0 to 18.5×10 –6 K –1 for x=0.6 at 30–900 °C. Among the LSCSbx compositions, the LSCSb0.2 exhibits the lowest polarization resistance ( R p ), which is merely 0.069 Ω cm 2 at 700 °C. The maximum power density of the cell with LSCSb0.2 cathode on 300 µm thick LSGM electrolyte attains 564 mW cm –2 at 850 °C, which is higher than that of SrCo 0.9 Sb 0.1 O 3– δ (SCSb) cathode. All of the results indicate that LSCSb0.2 is a promising material for application in IT–SOFCs cathodes. [ABSTRACT FROM AUTHOR]

Ba x Sr 1− x Co 0.9 Sb 0.1 O 3− δ (BSCSbx, x = 0.0–0.8) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). BSCSbx oxides are crystallized in a tetragonal structure with s.g. P4/mmm . XPS analysis shows that Ba doping reduces valence state of Co ions: Co in SrCo 0.9 Sb 0.1 O 3− δ is prone to Co 4+ , while Co in Ba doped SrCo 0.9 Sb 0.1 O 3− δ becomes more prone to Co 3+ . Oxygen deficiency δ increases with Ba doping even at high temperatures. Conductivity is found to decrease with Ba doping. Thermal expansion coefficient (TEC) decreases from 20.6 × 10 −6 K −1 for x = 0.0 to 18.4 × 10 −6 K −1 for x = 0.6 at 30–1000 °C. With increasing x from 0.0 to 0.6, polarization resistance ( R p ) decreases monotonously, and then increases with further increasing x. The lowest R p of 0.081 Ω cm 2 at 700 °C is obtained for BSCSb0.6 cathode. At 700–850 °C, the R p of BSCSb0.6 is mainly contributed from electron charge transfer; however, below 700 °C, ion charge transfer plays a more important role in R p . Maximum power densities of the cell with BSCSb0.6 cathode on 300-μm thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolyte attain 306–944 mW cm −2 at 700–850 °C. These results indicate that BSCSb0.6 is a promising cathode for application in IT-SOFC. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4Co0.9Nb0.1O3−δ (BSCN)–xGd0.1Ce0.9O1.95 (GDC) composites with various GDC contents (x = 0–40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (R p) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest R p of 0.042 Ω cm2 at 700 °C. The maximum power density of a cell with BSCN–20GDC cathode on 300 μm-thick GDC electrolyte achieves 460–880 mW cm−2 at 700–800 °C. The excellent electrochemical performance of BSCN–20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas. [ABSTRACT FROM AUTHOR]

PrBaCo 2– x Mo x O 5+ δ (PrBCM– x , x = 0.00–0.07) layered perovskites were evaluated as cathodes for IT–SOFCs. The Mo solid solution limit for PrBCM– x was up to x = 0.05. Mo doping in the PrBCM– x decreased the electrical conductivity, which may mainly be due to the disturbed ···Co–O–Co··· electron transport channels with Mo doping. The thermal expansion coefficients decreased from 21.0 × 10−6 K−1 at x = 0.00 to 19.0 × 10−6 K−1 at x = 0.03 and then to 18.1 × 10−6 K−1 at x = 0.05. Although a reduction in electrochemical performance with high–valence Mo doping into PrBaCo 2 O 5+ δ (PrBCO) was demonstrated, the reduced TECs and improved electrochemical stability were more attractive for the application of SOFC cathode. Electrochemical dynamic processes determined by EIS fitting indicated that Mo doping contributed to the rate–determining role of ion charge transfer in the oxygen reduction reaction and thus resulted in reduced electrochemical performance. By comprehensive consideration, the PrBCM–0.03 was confirmed as the most suitable cathode candidate for IT–SOFCs. The polarization resistance was 0.067 Ω cm2 at 700 °C for the PrBCM–0.03 cathode on Sm 0.2 Ce 0.8 O 1.9 (SDC) electrolyte. A single cell with PrBCM–0.03 cathode and 300 μm–thick SDC electrolyte showed a maximum power density of 339 mW cm−2 at 700 °C and almost no degradation in performance was detected after a 42 h testing. This study provides a preliminary basis for further research into high–valence ion doping in layered perovskite cathode materials. Image 1 • Mo doped PrBCM- x oxides with x = 0.00–0.07 were evaluated as IT-SOFC cathodes. • TECs of the PrBCM- x exhibit a decrease with increasing Mo. • The R p of PrBCM-0.03 cathode on SDC electrolyte attains 0.067 Ω cm2 at 700 °C. • Cell with PrBCM-0.03 cathode shows good power output and stability. • PrBCM–0.03 is concluded to be the most suitable cathode among PrBCM- x oxides. [ABSTRACT FROM AUTHOR]