“Post-hydrogenation” structural transformations from KHg₂- to Fe₂P-type in R(Cu,Ni)₂ hydrides (R = Ce, Pr, Nd)

Chem. Met. Alloys 3 (2010) 169-176

https://doi.org/10.30970/cma3.0155

A.B. RIABOV, R.V. DENYS, R. ČERNÝ, I.Yu. ZAVALIY

Hydrogenation of orthorhombic KHg₂-type R(Cu,Ni)₂ pseudobinary intermetallic compounds (R = Ce, Pr, Nd) was found to lead to the formation of an orthorhombic insertion-type hydride, which readily transforms into a hexagonal Fe₂P-type hydride. This “post-hydrogenation” structural transformation can be accelerated by heating in vacuum at 100-120°C and is accompanied by release of ¼ of the available hydrogen, as has been confirmed by PND studies. Further heating in vacuum leads to disproportionation of the hydride and recombination with recovery of the orthorhombic R(Cu,Ni)₂ compound after complete elimination of hydrogen from the material.

Repeated hydrogen absorption by Pr(Cu_0.75Ni_0.25)₂ after complete recombination during desorption, and after partial hydrogen release up to 120°C.

Keywords

Metal hydrides / Crystal structure / X-ray diffraction / Powder neutron diffraction