| The total conductivity of a polycrystalline CeO2-based electrolyte material(?t) is therefore the sum of its grain(?gi) and grain boundary(?gb) conductivities.For an extremely pure material, the depletion of oxygen vacancies near the grain-boundary is significant. On the other hand, Si O2 impurities even at low concentrations of hundreds of ppm deteriorate the grain boundary conduction to a great extent. The lanthanum gallate additive can act as a blocking agent against the leakage current generated by the doped-ceria electrolyte. The grain boundary conductivity increases markedly due to the presence of phase interface and the mitigation of the harmful effects from Si O2 impurity. Metal oxide additives MgO or SrO have indeed been shown to increase the ionic conductivity of CeO2-based electrolytes by scavenging SiO2 contamination. The effect of A/B site substituted LaGaO3 on the electrical properties of purity/impurity CeO2-based electrolytes can be investigated by synthesised CeO2-LSGM/LSG/LGM electrolytes.In this paper, The effect of LSGM on the structures, electrical properties and scavenger SiO2 of purity CeO2-based electrolytes and impurity CeO2-based electrolytes with Nd2O3-doped CeO2(Ce0.8Nd0.2O1.9, NDC)-SrO/MgO doped lanthanum gallate(La0.9Sr0.1Ga0.9Mg0.1O3-?, LSGM) was investigated. We futher discussed the effect of SrO/MgO doped LaGaO3(LSGM/LSG/LGM) on the structures, electrical properties and scavenger SiO2 of purity/ impurity CeO2-based electrolytes. We finally investigated the influence of different SrO and MgO mass ratio to the NDCSi systems, it can clear that the effect of the grain boundary scavenger of A-site(SrO) and B-site(MgO) substituted LaGaO3 to NDCSi systems and the relative strength of scavenging effect.(1)The impurities SiO2 reduce the total ionic conductivity of NDC by increasing the grain-boundary resistance therein. We can indicate that at a certain extent doping some LSGM to NDc enhances ionic conductivity and block off the electronic conduction.(2) The NDC-LSGM/LSG/LGM composite electrolytes were composed of the cubic fluorite structure and perovskite structure. The contribution of grain-boundary resistivity to the overall resistivity is significant.The LSGM/LSG/LGM additive can introduce large amount of phase interfaces, and mitigated the harmful effects from SiO2 impurity and thus the grain boundary conductivity increased markedly. Doping the A site of LaGaO3 with SrO proves more effective in this context than B-site substitution with MgO does.(3) The additives(LSG, LGM, or LSGM) alleviate this effect by concentrating SiO2 at the grain boundaries and pinning or fixing the impurities to their SrO and/or MgO components, leading to the formation of more conductive phases. Doping the La site ofLaGaO3 with SrO proves more effective in this context than Ga-site substitution with MgO does. The greater scavenging ability SrO stems from its greater chemical affinity for SiO2.Since the LSGM additive combines the benefits of LSG and LGM, NDCSi-LSGM exhibits the highest conductivities(grain-boundary and total) of the samples investigated here.(4) The SrO and MgO addition could not only increase the density, but also increase the grain boundary and total conductivity of the NDCSi. SrO and MgO can mitigated or scavenged the harmful effects from the SiO2 impurity, and with the increase of the doping amount, the removal effect is more obvious. SrO is a better scavenger materials compared with MgO. |
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