Phase diagram of La2NiO4+δ (0 ≤ δ ≤ 0.18) II. Thermodynamics of excess oxygen, phase transitions (0.06 ≤ δ < 0.11) and phase segregation (0.03 ≤ 6 < 0.06)
Phase diagram of La2NiO4+δ (0 ≤ δ ≤ 0.18) II. Thermodynamics of excess oxygen, phase transitions (0.06 ≤ δ < 0.11) and phase segregation (0.03 ≤ 6 < 0.06)
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La2NiO4+δ (0 ≤ δ ≤ 0.18) 相图 二、过量氧、相变 (0.06 ≤ δ < 0.11) 和相偏析 (0.03 ≤ 6 < 0.06) 的热力学
DOI：
10.1016/0921-4534(95)00798-9
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发表时间：
1996
影响因子：
1.7
通讯作者：
Y. Ueda
中科院分区：
文献类型：
--
作者：
H. Tamura;A. Hayashi;Y. Ueda
用热重法（TG）和原位X射线粉末衍射法研究了La 2NiO 4+ δ中氧的非化学计量比和结构相变。通过对TG数据的分析，提出了氧的存在形式为带双电荷的O2-。在0.06=< δ< 0.11的范围内发现了从四相I_4/mmm到正交相Fmmm的转变，并表现出明显的时间依赖性。对于0.03=< δ< 0.06，观察到来自四氢呋喃I4/mmm的假四氢呋喃相的相分离。当0=< δ=< 0.18时，提出了La 2NiO 4+ δ的平衡相图.根据各正交相的正交性随温度的变化关系，讨论了相变的特征。
Oxygen nonstoichiometry and structural phase transitions in La 2 NiO 4+ δ were studied by thermogravimetry (TG) and in-situ X-ray powder diffraction. Doubly charged O 2-ions are proposed as the species of the excess oxygen from thermodynamical analysis of TG data. A transition from tetragonal I4/mmm to orthorhombic Fmmm phase was found in the wide range of 0.06=< δ< 0.11, which showed a significant time dependence. The phase segregation of pseudo-tetragonal phase from tetragonal I4/mmm was observed for 0.03=< δ< 0.06. An equilibrium phase diagram of La 2 NiO 4+ δ is proposed for 0=< δ=< 0.18. The character of the phase transitions is discussed in the light of the temperature dependence of the orthorhombicity in each orthorhombic phase.