Structural and hydriding properties of MgYNi 4: : A new intermetallic compound with C15 b-type Laves phase structure

Abstract

A new intermetallic compound MgYNi 4 with C15 b(AuBe 5)-type Laves phase structure was successfully synthesized by both mechanical milling and casting methods. The structural and hydriding properties of the samples were examined by X-ray diffraction measurement, thermal analysis and hydrogen pressure–composition ( p– c) isotherm measurement. The lattice parameter of MgYNi 4 was estimated to be a=0.701 nm, which is ca. 2% smaller than that of YNi 2. A plateau (miscibility-gap) pressure was clearly observed in the p– c isotherm during the dehydriding process of the sample synthesized by casting. The maximum hydrogen content is ∼1.05 mass% (H/M∼0.6) under a hydrogen pressure of 4.0 MPa at 313 K, and the enthalpy of hydride formation was calculated to be −35.8 kJ/mol H 2. The study in this paper reveals, for the first time, an application potential of MgNi 2-based Laves phase structure for practical use as hydrogen storage and transport materials.