Crystallographic hydride phase analysis and hydrogenation properties of Gd2Co7 with Ce2Ni7- and Er2Co7-type structures

Abstract

We synthesized an intermetallic compound Gd2Co7 with Ce2Ni7- and the Er2Co7-type structures. Gd2Co7 with a Ce2Ni7-type structure was stable at 1523 K. The refined lattice parameters were a = 0.5026(1) nm and c = 2.4266(6) nm. The pressure-composition (P–C) isotherm of Ce2Ni7-type Gd2Co7 indicated that reversible hydrogen capacity reached 0.61 H/M (0.76 mass%), and two plateaus were observed in the absorption-desorption process. The crystal structures of both Gd2Co7H2.5 and Gd2Co7H5.5 were determined to be Ce2Ni7-type by X-ray diffraction.Gd2Co7 with Er2Co7-type structure is stable at temperatures below 1473 K. The refined lattice parameters were a = 0.5029(1) nm and c = 3.6403(9) nm. The determined crystal structure of Gd2Co7H2.3 and Gd2Co7H5.4 was Er2Co7-type. The P–C isotherm of Er2Co7-type Gd2Co7 was similar to that of Ce2Ni7-type Gd2Co7. In this study, the P–C isotherms of a polymorphic binary alloy with Ce2Ni7-type and Er2Co7-type structures were obtained for the first time.