Abstract
We investigated the phase stability of Nd2Co7 with 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 Nd2Co7 when the alloy was annealed at 1373 K, followed by quenching in ice water. The phase transformation follows the order: hexagonal Nd2Co7 (space group P63/mmc) → hexagonal Nd2Co7H2.7 (space group P63/mmc) → orthorhombic Nd2Co7H8.1 (space group Pbcn), upon hydrogen absorption. Anisotropic lattice expansion along the c axis was observed in Nd2Co7H2.7. The unit cell of Nd2Co7H8.1 underwent isotropic expansion along the a, b, and c axes. 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.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
