Materials Science, California Institute of Technology, Pasadena, CA, USA.
Phys Chem Chem Phys. 2013 Feb 21;15(7):2466-72. doi: 10.1039/c2cp43036c. Epub 2013 Jan 15.
Columnar thin films of undoped ceria were grown by metal-organic chemical vapor deposition. The films, deposited on Pt-coated MgO(100) substrates, display a columnar microstructure with nanometer scale grain size and ~30% overall porosity. Through-plane (thickness mode) electrical conductivity was measured by AC impedance spectroscopy. Proton conduction is observed below 350-400 °C, with a magnitude that depends on gas-phase water vapor pressure. The overall behavior suggests proton transport that occurs along exposed grain surfaces and parallel grain boundaries. No impedance due to grain boundaries normal to the direction of transport is observed. The proton conductivity in the temperature range of 200-400 °C is approximately four times greater than that of nanograined bulk ceria, consistent with enhanced transport along aligned grain surfaces in the CVD films.
采用金属有机化学气相沉积法生长了未掺杂氧化铈的柱状薄膜。沉积在 Pt 涂覆的 MgO(100)衬底上的薄膜具有柱状微观结构，纳米级晶粒尺寸和~30%的总孔隙率。通过面内（厚度模式）交流阻抗谱测量了薄膜的交流电导率。在 350-400°C 以下观察到质子传导，其大小取决于气相水蒸气压。整体行为表明质子沿着暴露的晶粒表面和晶界平行方向传输。未观察到垂直于传输方向的晶界的阻抗。在 200-400°C 的温度范围内，质子电导率比纳米晶粒氧化铈大约四倍，这与 CVD 薄膜中沿晶面取向增强的传输一致。
