Keeping the stoichiometry at the optimal value required for electrical conduction throughout polycrystalline ceramics is crucial for various polycrystalline oxygen ion conductors. Using the photoluminescence spectrum of Eu³⁺ as a structural probe, the dependence between composition uniformity and conductivity was confirmed. We found that, for apatite La_9.67×0.99Eu_9.67×0.01Si₆O_26.505 (LSO) oxygen ion conductors synthesized by glycine nitrate combustion method, higher glycine content enhances the La/Si ratio uniformity, thereby improving the bulk conductivity. Surprisingly, thermal diffusion even at 1550°C cannot achieve uniform distribution when the precursor materials are not sufficiently homogeneous. Slight non-uniformity in the La/Si ratio is beneficial for impurities aggregation at high-density grain boundary regions, thereby alleviating the blocking effect of grain boundary on oxygen ion conduction. Both the bulk and total conductivities are higher than the best reported values in polycrystalline apatite by optimizing the La/Si ratio uniformity. The insight gained in this work is beneficial for enhancing conductivity by modulating crystalline homogeneity, and it facilitates further enhancement of ionic conductivity through cations doping for various polycrystalline oxygen ion conductors.

中文翻译：

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通过调节结晶均匀性来优化氧离子电导率


将化学计量保持在整个多晶陶瓷导电所需的最佳值对于各种多晶氧离子导体至关重要。使用 Eu³⁺ 的光致发光光谱作为结构探针，证实了成分均匀性和电导率之间的依赖性。我们发现，对于甘氨酸硝酸盐燃烧法合成的磷灰石 La_9.67×0.99Eu_9.67×0.01Si₆O_26.505 （LSO） 氧离子导体，较高的甘氨酸含量增强了 La/Si 比的均匀性，从而提高了体电导率。令人惊讶的是，当前驱体材料不够均匀时，即使在 1550°C 的温度下，热扩散也无法实现均匀分布。La/Si 比值的轻微不均匀性有利于高密度晶界区域的杂质聚集，从而减轻晶界对氧离子传导的阻塞作用。通过优化 La/Si 比率均匀性，体积和总电导率都高于多晶磷灰石中的最佳报告值。这项工作中获得的见解有利于通过调节晶体均匀性来提高电导率，并且它有助于通过阳离子掺杂各种多晶氧离子导体来进一步增强离子电导率。