The relationship between the thermoelectric power and phase structure in AB2 hydrogen storage materials

The phase structure during the hydrogenation of AB(2)-type hydrogen storage intermetallic alloys has been investigated using the compound of Zr0.9Ti0.1CrxFe2-x as a typical representative type of AB(2) system. The as-received compounds of Zr0.9Ti0.1CrxFe2-x with x=0.6, 0.8 and 1.0 are all pure C-14 Laves phase, a hexagonal structure. With an increasing amount of the stored hydrogen, the thermoelectric power (TEP) of these compounds increase. The amount of stored hydrogen alters the electronic states in the alloys, which can be distinguished from the variation of the results of the thermoelectric power measurements. The corresponding TEP is found to have the relationship with phase structure of the alloy hydrides under hydrogenation. The relationship of the Seebeck coefficient and the thermodynamics of hydrogenation are derived by considering the Seebeck effect as the external work. The variation in alloy composition has been represented by the d-shell electronic concentration (DEC) number. (C) 2004 Elsevier B.V. All rights reserved.