Phase transformation of hydride-phase Nd2Co7 with superlattice structure
Phase transformation of hydride-phase Nd2Co7 with superlattice structure
复制标题
超晶格结构氢化物相Nd2Co7的相变
DOI：
10.1016/j.jssc.2022.123575
复制
发表时间：
2022
影响因子：
3.3
通讯作者：
Kazuhiro Mori
中科院分区：
文献类型：
--
作者：
Kenji Iwase;Yugo Honjyo;Kazuhiro Mori
研究了具有超晶格结构的Nd 2Co 7的相稳定性、吸放氢性能以及吸放氢过程中的相转变。结果表明，在1273 K以下退火样品中Ce 2Ni 7型和Gd 2Co 7型结构共存。当温度高于1323 K时，Gd 2Co 7型相消失。我们成功地合成了一个很大的单相Ce 2Ni 7型Nd 2Co 7合金时，在1373 K退火，然后在冰水中淬火。吸氢后的相变顺序为：六方晶系Nd 2Co 7（空间群P63/mmc）→六方晶系Nd2Co7H2.7（空间群P63/mmc）→正交晶系Nd2Co7H8.1（空间群Pbcn）。观察到Nd_2Co_7 H_（2.7）的晶格沿轴向沿着各向异性膨胀。Nd_2Co_7 H_（8.1）晶胞沿沿着a、B和cax方向各向同性膨胀。然而，MgZn 2型电池、CaCu 5型电池I和CaCu 5型电池II的体积膨胀不均匀，分别为36.0%、8.9%和13.0%。
We investigated the phase stability of Nd2Co7with a superlattice structure, its hydrogenation properties, and phase transformation during hydrogen absorption–desorption process. The results showed that Ce2Ni7-type and Gd2Co7-type structures coexisted in the annealed sample up to 1273 K. The Gd2Co7-type phase disappeared at temperatures above 1323 K. We successfully synthesized a largely single-phase Ce2Ni7-type Nd2Co7when the alloy was annealed at 1373 K, followed by quenching in ice water. The phase transformation follows the order: hexagonal Nd2Co7(space groupP63/mmc) → hexagonal Nd2Co7H2.7(space groupP63/mmc) → orthorhombic Nd2Co7H8.1(space groupPbcn), upon hydrogen absorption. Anisotropic lattice expansion along thecaxis was observed in Nd2Co7H2.7. The unit cell of Nd2Co7H8.1underwent isotropic expansion along thea,b, andcaxes. However, the volume expansions of the MgZn2-type cell, CaCu5-type cell I, and CaCu5-type cell II were uneven at 36.0%, 8.9%, and 13.0%, respectively.