[论文解读] Protons in lattice confinement: Static pressure on the Y-substituted, hydrated BaZrO3 ceramic proton conductor decreases proton mobility

Qianli Chen, Artur Braun+4 more|arXiv (Cornell University)|Jun 6, 2011

Advancements in Solid Oxide Fuel CellsMaterials Science参考文献 18被引用 20

一句话总结

本研究在高静态压力（1–2 GPa）下研究了钇掺杂、含水的BaZrO3陶瓷质子导体中的质子输运。通过电导率谱分析发现，随着压力增加，由于晶格压缩，体相晶格中的质子迁移率降低；而晶界电阻随压力升高而降低，这是由于压力诱导的致密化所致，表明晶格膨胀可增强薄膜应用中的质子电导率。

ABSTRACT

Yttrium substituted BaZrO3, with nominal composition BaZr0.9Y0.1O3, a ceramic proton conductor, was subject to impedance spectroscopy for temperatures 300 K < T < 715 K at mechanical pressures 1 GPa < p < 2 GPa. The activation energies Ea of bulk and grain boundary conductivity from two perovskites synthesized by solid-state reaction and sol-gel method were determined under high pressures. At high temperature, the bulk activation energy increases with pressure by 5% for sol-gel derived sample and by 40% for solid-state derived sample. For the sample prepared by solid-state reaction, there is a large gap of 0.17 eV between the activation energy at 1.0 GPa and > 1.2 GPa. The grain boundary activation energy is around a factor two times as that of the bulk, and it reaches a maximum at 1.25 - 1.5 GPa, and then decrease as the pressure increases, indicating higher proton mobility in the grain boundaries at higher pressure. Since this effect is not reversible, it is suggested that the grain boundary resistance decreases as a result of pressure induced sintering. The steady increase of the bulk resistivity upon pressurizing suggests that the proton mobility depends on the space available in the lattice. In return, an expanded lattice with a/a0 > 1 should thus have a lower activation energy, suggesting that thin films expansive tensile strain could have a larger proton conductivity with desirable properties for applications.

研究动机与目标

• 理解静态压力对钇取代、含水的BaZrO3陶瓷质子导体中质子电导率的影响。
• 确定晶格受限对体相和晶界区域质子迁移能垒的影响。
• 比较溶胶-凝胶法与固相反应法合成的BaZrO3样品在压力下的质子电导率行为差异。
• 探讨晶格应变对薄膜应用中质子电导率的影响。

提出的方法

• 在1–2 GPa的静态压力下，对钇掺杂的BaZrO3样品在300 K至715 K的温度范围内进行了电导率谱分析。
• 采用两种合成方法——固相反应法和溶胶-凝胶法——以比较微观结构对质子输运的影响。
• 从压力下电导率数据的阿伦尼乌斯图中提取体相和晶界电导率的活化能。
• 通过活化能和电阻率趋势的变化推断压力引起的结构变化。
• 通过测试电阻变化的可逆性，评估永久性结构改性的可能性。

实验结果

研究问题

• RQ1 随着静态压力增加，钇掺杂BaZrO3体相晶格中质子电导的活化能如何变化？
• RQ2 晶界质子电导率的压强依赖性如何？其行为是可逆还是不可逆的？
• RQ3 不同的合成方法（溶胶-凝胶法与固相反应法）如何影响质子迁移率的压强响应？
• RQ4 晶格膨胀是否可降低活化能并增强质子导体中的质子电导率？

主要发现

• 对于溶胶-凝胶法制备的样品，体相活化能增加了5%，而固相反应法制备的样品增加了40%，表明晶格压缩导致质子迁移率降低。
• 在固相反应样品中，活化能在1.0 GPa至1.2 GPa之间出现0.17 eV的急剧上升，提示发生关键的结构转变。
• 晶界活化能在1.25–1.5 GPa之间达到峰值，随后随压力进一步升高而下降，表明压力诱导致密化改善了质子迁移率。
• 晶界电阻的降低是不可逆的，证实了压力作用导致了永久性的微观结构变化。
• 体相电阻率随压力持续上升，表明质子迁移率受晶格空间可用性的限制，暗示拉伸应变下的晶格膨胀（如在薄膜中）可能提升电导率。