双钙钛矿型LnBaCo2O5.5+δ薄膜中氧空位的超快逐层原子交换扩散

Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

作者信息

Bao Shanyong, Ma Chunrui, Chen Garry, Xu Xing, Enriquez Erik, Chen Chonglin, Zhang Yamei, Bettis Jerry L, Whangbo Myung-Hwan, Dong Chuang, Zhang Qingyu

机构信息

1] Department of Physics and Astronomy, University of Texas at San Antonio, TX 78249, USA [2] Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024, China.

Department of Physics and Astronomy, University of Texas at San Antonio, TX 78249, USA.

出版信息

Sci Rep. 2014 Apr 22;4:4726. doi: 10.1038/srep04726.

DOI:10.1038/srep04726

PMID:24751601

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3994446/

Abstract

Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800 °C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

摘要

通过在250至800°C温度范围内仔细监测氧化气体（O₂）和还原气体（H₂）切换流动下的电阻变化，研究了双钙钛矿LnBaCo₂O₅.₅+δ（LnBCO）单晶薄膜（Ln = Er，Pr；-0.5 < δ < 0.5）中的表面交换和氧空位扩散动力学。在小于0.1 s的时间内发现电阻变化ΔR有三到四个数量级的巨大变化，并且在ΔR与t的曲线中电阻变化率呈现快速振荡行为，这表明LnBCO薄膜中氧空位与氧/氢原子的交换扩散遵循逐层氧空位交换机制。第一性原理密度泛函理论计算表明，氢原子以与氧形成O-H键的形式存在于LnBCO中。这种前所未有的振荡现象为逐层氧空位交换扩散机制提供了首个直接实验证据。