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.

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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(La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−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 cm 2 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 ∼10 times from 0.22 Ω cm 2 of the pristine cell to 2.18 Ω cm 2 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.

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