Effect of oxygen on the microstructure and hydrogen storage properties of V–Ti–Cr–Fe quaternary solid solutions

Abstract The effect of low ( 40 Fe 8 Ti 26 Cr 26 , was investigated by means of XRD, SEM, TEM and pressure-composition isotherms. A high oxygen concentration in the vanadium raw metal led to the formation of an oxygen-rich secondary phase isostructural with α-Ti. The lattice parameter of the BCC main phase of the high-oxygen sample was reduced to 3.0141 (3) A compared to 3.0308 (2) A for the low-oxygen sample. As a result of the high oxygen content the equilibrium hydrogen pressure of the material was increased from 1 MPa to 4 MPa. Deoxidization through the addition of 1 at% rare earth metal could be achieved. The lattice constant of the deoxidized sample was 3.0297 (3) A, and the thermodynamic properties were also the same as in case of the low-oxygen sample.