RESUMEN
To improve the performance of the Ce0.8Gd0.2O2-δ (GDC) electrolyte in a solid oxide fuel cell, it is necessary to block the electronic conduction due to Ce3+/Ce4+ transitions occurring at elevated temperatures. In this work, a GDC/ScSZ double layer consisting of 50 nm GDC and 100 nm Zr0.8Sc0.2O2-δ (ScSZ) thin films were deposited on a dense GDC substrate by the pulsed laser deposition (PLD) technology. The effectiveness of the double barrier layer in blocking the electronic conduction of the GDC electrolyte was investigated. The results showed that the ionic conductivity of GDC/ScSZ-GDC was slightly lower than that of GDC in the temperature range of 550-750 °C, but the difference gradually decreased with the increase in temperature. At 750 °C, the conductivity of GDC/ScSZ-GDC was 1.54 × 10-2 S·cm-1, which was almost the same as that of GDC. The electronic conductivity of GDC/ScSZ-GDC was 1.28 × 10-4 S·cm-1, which was lower than that of GDC. The conductivity results showed that the ScSZ barrier layer can reduce electron transfer effectively. More obviously, the open-circuit voltage and the peak power density of the (NiO-GDC)|GDC/ScSZ-GDC|(LSCF-GDC) cell were higher than those of the (NiO-GDC)|GDC|(LSCF-GDC) cell in the temperature range of 550-750 °C. The superior performance of the GDC/ScSZ-GDC electrolyte is attributed to the ScSZ thin layer, which is effective in blocking the electronic conduction of the GDC electrolyte.
RESUMEN
As a device for direct conversion of chemical energy into electrical energy, the solid oxide fuel cell (SOFC) contributes positively to the sustainable development strategy. However, the commercialization of fuel cells is still impeded by severe cathode degradation caused by its limited stability at operating temperatures and being prone to Cr-poisoning from Cr-containing alloy interconnectors commonly used in these cells. This paper reports the development of a high-durability Ba-doped LSCF(La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode material under realistic fuel cell operating conditions in the presence of the Cr alloy. In particular, when tested in a symmetrical cell constructed of Ba-doped LSCF, the polarization resistance of the cell remains very low at 0.06 Ω cm2 after being tested at 800 °C for 120 h exposed to Cr in 3% humidified air. In contrast, for the undoped LSCF under the same testing conditions, the polarization resistance of the cell increases â¼10 times from 0.22 Ω cm2 of the pristine cell to 2.18 Ω cm2 after Cr-exposure testing. Furthermore, when tested in an anode-supported complete cell as a cathode under typical SOFC operation conditions at 750 °C, the cell with the Ba-doped LSCF cathode displays significantly low degradation rates of 0.00056% h-1 (without Cr) and 0.00310% h-1 (with Cr); both are much lower than that of the cell using the undoped LSCF cathode (0.00124% h-1 without Cr and 0.01082% h-1 with Cr). This enhanced durability and Cr-tolerance exhibited by the Ba-doped LSCF cathode stem from its higher crystal structure stability and improved chemical resistance compared to undoped LSCF.
RESUMEN
In this study, the grain growth behaviour of ZnO-V2O5-based ceramics with 0.25-0.75 mol% additions of PrMnO3 was systematically investigated during sintering from 850 °C to 925 °C. with the aim to control the ZnO grain size for their application as varistors. It was found that with the increased addition of PrMnO3, in addition to the decrease in the average grain size, the grain size distribution also narrowed and eventually changed from a bimodal to unimodal distribution after a 0.75 mol% PrMnO3 addition. The grain growth control was achieved by a pinning effect of the secondary ZnCr2O4 and PrVO4 phases at the ZnO grain boundaries. The apparent activation energy of the ZnO grain growth in these ceramics was found to increase with increased additions of PrVO4, hence the observed reduction in the ZnO grain sizes.
