A位掺杂Ru对SPS制备LaCrO3陶瓷导电性的影响及其作为熔盐中惰性阳极的可行性

Influence of Ru doping on the conductivity of LaCrO3 ceramic prepared by SPS and the feasibility of the doped ceramic for an inert anode of molten salt electrolysis

    摘要
  • 摘要: 铬酸镧（LaCrO3）陶瓷材料在高温热电和固体氧化物燃料电池（SOFC）等领域具有广泛的应用价值，然而其烧结性能差、导电率低等不足却限制了LaCrO3陶瓷的高性能应用。针对上述问题，采用放电等离子烧结（SPS）方式制备致密的LaCrO3块体。同时，通过A位掺杂Ru元素，以期实现高电导率的掺杂态铬酸镧（La1−xRuxCrO3）致密陶瓷。所得样品的X射线衍射（XRD）及扫描电子显微（SEM）分析结果表明，无论A位Ru元素含量多少（x=0～0.25， x为Ru的原子含量），SPS所得样品均为单相钙钛矿结构，且具有较高的致密度。此外，高温电导率测试结果显示，掺杂态La1−xRuxCrO3的电导率随着温度和Ru掺杂量的增加而增加。同时，掺杂前后La1−xRuxCrO3导电性均满足Arrhenius公式，且掺杂态La1−xRuxCrO3陶瓷的电导活化能明显低于未掺杂的LaCrO3陶瓷。随后，将La1−xRuxCrO3置于800 °C熔融CaCl2熔体中，研究其作为熔盐电解用惰性阳极材料的可行性。结果显示，掺杂态La1−xRuxCrO3具有较高的抗熔盐化学腐蚀性，然而其抗热振性较差，电解之后出现明显的表层机械脱落现象。上述结果表明，掺杂态La1−xRuxCrO3具备作为惰性析氧阳极材料的化学稳定性，然而需要进一步提高其热稳定性才能适用于熔盐电解用惰性阳极。

     

    Abstract: LaCrO3 ceramic is a promising function material in areas such as high temperature piezoelectric materials and solid oxide fuel cells (SOFC). However, its practical applications are limited by fatal flaws including their low density and poor conductivity. To address these challenges, spark plasma sintering (SPS) was used to prepare the high-density LaCrO3 ceramic. Additionally, Ru, a multivalent metallic element, was doped in the A site of the LaCrO3 ceramic to investigate the conductivity of the La1−xRuxCrO3 (x=0−0.25). X-ray power diffraction (XRD) results and scanning electron microscope images show that the sintered La1−xRuxCrO3 ceramic has a single perovskite phase and high density. The characteristic peak shifting observed in the XRD pattern indicates that the Ru element has been successfully doped in the A site of the LaCrO3 ceramic. Whereas, the results of the Energy dispersive spectrometer (EDS) prove that there is no obvious change in the Ru content before and after sintering by SPS, which indicates that no actual Ru loss can occur during the SPS process at 1600 °C. Moreover, the conductivity of the sintered La1−xRuxCrO3 increases with increasing Ru content and temperature. The results also indicate that there is good linear relationship between ln(σT) and 1/T, demonstrating that the conductivity of the La1−xRuxCrO3 obeys the Arrhenius law. The activation energy of the doped La1−xRuxCrO3 ceramic is smaller than that of the LaCrO3 ceramic. Lastly, the feasibility of the application of doped La1−xRuxCrO3 ceramics as the inert anode of molten salt electrolysis in CaCl2 melt has been investigated at the temperature of 800 °C. These findings demonstrate that the doped La1−xRuxCrO3 ceramic has an excellent chemical corrosion-resistant property. However, it has poor thermal stability, which inhibits its application as an inert anode. Future studies focusing on the improvement of the heat-shock resistance and elucidating the corrosion resistance mechanism of La1−xRuxCrO3 in CaCl2 melt is recommended.

     

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