Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-Ku, Yokohama, Kanagawa 226-8502, Japan.
J Am Chem Soc. 2010 Feb 24;132(7):2385-92. doi: 10.1021/ja909820h.
We have investigated in situ the crystal structure, oxygen diffusion path, oxygen permeation rate, and electrical conductivity of a doped praseodymium nickel oxide, Pr(2)NiO(4)-based mixed conductor, (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+delta) (PLNCG) in air between 27 degrees C and 1015.6 degrees C. The PLNCG has a tetragonal I4/mmm K(2)NiF(4)-type structure which consists of a (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit and a (Pr(0.9)La(0.1))O rock salt unit in the whole temperature range. Both experimental and theoretical electron density maps indicated two-dimensional networks of (Ni(0.74)Cu(0.21)Ga(0.05))-O covalent bonds in PLNCG. Highest occupied molecular orbitals (HOMO) in PLNCG demonstrate that the electron-hole conduction occurs via Ni and Cu atoms in the (Ni(0.74)Cu(0.21)Ga(0.05))-O layer. The bulk oxygen permeation rate was high (137 mumol cm(-2) min(-1) at 1000 degrees C), and its activation energy was low (51 kJ mol(-1) at 950 degrees C). The Rietveld method, maximum-entropy method (MEM), and MEM-based pattern fitting analyses of neutron and synchrotron diffraction data indicate a large anisotropic thermal motion of the apical O2 oxygen at the 4e site (0, 0, z; z approximately 0.2) in the (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit. Neutron and synchrotron diffraction data and theoretical structural optimization show the interstitial oxygen (O3) atom at (x, 0, z) (x approximately 0.6 and z approximately 0.2). The nuclear density analysis indicates that the bulk oxide-ion diffusion, which is responsible for the high oxygen permeation rate, occurs through the interstitial O3 and anisotropic apical O2 sites. The nuclear density at the bottleneck on the oxygen diffusion path increases with temperature and with the oxygen permeation rate. The activation energy from the nuclear density at the bottleneck decreases with temperature, which is consistent with the decrease of the activation energy from oxygen permeation rate. The extremely low activation energy (12 kJ mol(-1) at 900 degrees C) from the nuclear density at the bottleneck indicates possible higher bulk oxygen permeation rates in quality single crystals and epitaxial thin films.
我们在空气氛围中研究了掺杂镨镍氧化物，即 Pr(2)NiO(4)-基混合导体 (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+δ) (PLNCG) 的原位晶体结构、氧扩散路径、氧渗透速率和电导率，温度范围为 27 摄氏度至 1015.6 摄氏度。PLNCG 具有四方 I4/mmm K(2)NiF(4)-型结构，由 (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) 钙钛矿单元和 (Pr(0.9)La(0.1))O 岩盐单元组成。在整个温度范围内，实验和理论电子密度图都表明了 PLNCG 中 (Ni(0.74)Cu(0.21)Ga(0.05))-O 共价键的二维网络。PLNCG 中的最高占据分子轨道（HOMO）表明，电子-空穴通过 (Ni(0.74)Cu(0.21)Ga(0.05))-O 层中的 Ni 和 Cu 原子发生传导。体氧渗透速率高（1000°C 时为 137 µmole cm(-2) min(-1)），其激活能低（950°C 时为 51 kJ mol(-1)）。Rietveld 法、最大熵法（MEM）和基于 MEM 的图谱拟合分析中子和同步辐射衍射数据表明，在 (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) 钙钛矿单元中，4e 位（0，0，z；z 约为 0.2）的氧原子具有较大的各向异性热运动。中子和同步辐射衍射数据和理论结构优化表明，间隙氧（O3）原子位于（x，0，z）（x 约为 0.6 和 z 约为 0.2）。核密度分析表明，负责高氧渗透速率的体氧化物离子扩散通过间隙 O3 和各向异性的氧原子发生。氧扩散路径瓶颈处的核密度随温度和氧渗透速率的增加而增加。核密度瓶颈处的激活能随温度降低而降低，这与氧渗透速率的激活能降低一致。核密度瓶颈处的极低激活能（900°C 时为 12 kJ mol(-1)）表明在质量单晶和外延薄膜中可能具有更高的体氧渗透速率。
