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发布日期:2013-12-18   浏览次数:

题目:双钙钛矿LaBaCo2O5.5薄膜的反常物理性质(Anomalous Physical Properties of Double-Perovskites LaBaCo2O5.5 Thin Films)


时间:12月19日 9:30



主讲简介:陈充林,University of Texas at San Antonio教授,研究专长:多功能氧化物薄膜的外延生长,纳米材料制备,表面和界面物理化学性能等。Prof. Chonglin Chen已在包括Nature, Physical Review Letters, Applied Physics Letters, Nano Letters等著名期刊发表论文150余篇,并在国际和国内会议作超过200次邀请报告。相关研究工作得到了NSF-NIRT和CMS项目,美国能源部,美国陆军研究办公室,德克萨斯州高级研究计划等的支持。在多种国际会议中担任国际顾问委员会成员,在美国陶瓷学会,材料科学与工程等学术研讨会中单位主席和/或共同主席。

主讲内容:Ferromagnetic thin films of the A-site nano-ordered double perovskite LaBaCo2O5.5+ (LBCO) were grown on various substrates. The as-grown films have an excellent epitaxial behavior with atomically sharp interfaces. A giant magnetoresistance of 54 % was achieved at 40 K under 7 T with anomalous magnetic properties. Superfast chemical exchange dynamic behavior was discovered on the surfaces of the highly epitaxial thin films of single-crystalline cobalt double-perovskites (LnBCO). The exchange diffusion of oxygen and hydrogen through these films were examined by measuring their resistance R under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250~800 C. These films were found to exhibit ultrafast oxygen/hydrogen diffusivity and high sensitivity to redox environments. Their resistance R changes by three to four orders of magnitude in less than 0.1 s. When measured as a function of the gas flow time t, these LnBCO films show fast oscillations in the R vs. t plots with time period shorter than 1 s during the oxidation cycle under O2. This unprecedented oscillation phenomenon provides the first direct experimental evidence that oxygen/hydrogen atoms diffuse through the LnBCO thin films layer by layer via the oxygen-vacancy-exchange mechanism. The excellent chemical dynamics and ultrafast layer-by-layer oxygen vacancy exchange diffusion suggest that the as-grown LnBCO can be an excellent candidate for energy harvest and chemical sensor developments.


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