Relationships between the electrical resistivity and the metal hydride phases

Electrical resistivitiy of the unstable metal hydrides LaNi 5 H x and LaCo 5 H x has been measured in situ by a newly developed method where the samples are under the influence of mechanical stress. An activated sample does not give the bulk resistivity of the hydride, but the resistivity change with hydrogen pressure or temperature is correlated with the transformation of hydride phases. The resistivity of the bulk hydride is tolerably obtained in the first absorption of hydrogen for a virgin sample. The resistivity at 323 K is 1.3, 15.3 and 8.5 μΩm for the metal phase ( x = 0), the α phase ( x ⋍ 0.6) and the β phase ( x = 6.7) of LaNi 5 H x , and 1.5, 11.5 and 18.8 μΩm for the metal phase ( x = 0), the β phase ( x = 3.4) and the γ phase ( x = 4.3) of LaCo 5 H x , respectively. These resistivity changes with hydrogen composition are interpreted in relation to disordered-ordered arrangment of hydrogen.