Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea.
Phys Chem Chem Phys. 2010 May 14;12(18):4704-13. doi: 10.1039/b918329a. Epub 2010 Mar 18.
La(2)NiO(4+delta) is an oxygen excess compound (delta > 0) with oxygen interstitials (O(i) and holes (h*) in majority, which deviates positively from the ideal-dilute-solution behavior of defects. It was earlier attempted to interpret this positive deviation by taking into account the activity coefficients of both O(i) and h*. In this work, we examined the nonstoichiometry, electrical conductivity, and thermopower against oxygen activity in the entire stability range of the oxide at 800 degrees , 900 degrees and 1000 degrees C, respectively. It has been found that the positive deviation is ascribed essentially to the hole degeneracy and quantitatively described by using the Joyce-Dixon approximation of the Fermi-Dirac integral. Consequently evaluated are the effective density of states of the valence band (20.3 <or= log(N(v)/cm(-3)) <or= 20.5), the Fermi energy relative to the valence band edge (-5 <or= (E(F)-E(V))/kT<or= 1.5), and the effective mass (1.2<or=m(h)*/m(0)<or=1.3)), mobility (0.14-0.17 cm(2) V(-1) s(-1)), and reduced heat-of-transport (ca. 0.02 eV) of holes. The stability limit of the oxide is also evaluated and compiled together with the reported values.
La(2)NiO(4+δ) 是一种氧过剩化合物（δ＞0），其中存在大量的氧间隙（O(i) 和空穴（h*），这使其偏离了理想稀溶液中缺陷的行为。早期曾尝试通过考虑 O(i) 和 h的活度系数来解释这种正偏差。在这项工作中，我们分别在 800°C、900°C 和 1000°C 的整个氧化物稳定范围内，针对氧活度研究了非化学计量比、电导率和热电势。结果发现，正偏差主要归因于空穴简并度，并通过使用费米-狄拉克积分的 Joyce-Dixon 逼近来定量描述。因此，我们评估了价带的有效态密度（20.3≤log(N(v)/cm(-3))≤20.5）、费米能级相对于价带边缘的位置（-5≤(E(F)-E(V))/kT≤1.5）以及空穴的有效质量（1.2≤m(h)/m(0)≤1.3）、迁移率（0.14-0.17 cm(2) V(-1) s(-1)）和空穴的热输运降低量（约 0.02 eV）。我们还评估了氧化物的稳定极限，并与报道的值一起进行了汇编。
