Effects of the Mn substitution on microstructures and hydrogen absorption/desorption properties of LaNi3 8Al1 2-xMnx (x = 0 2 0 4 0 6) hydrogen storage alloys were investigated The pressure composition (PC) isotherms and absorption kinetics were measured in a temperature range of 433 K <= T <= 473 K by the volumetric method XRD analyses showed that with the increase of the Mn content in the LaNi3 8Al1 2-xMnx alloys the lattice parameter a was decreased c increased and the unit cell volume V reduced It was found that the absorption/desorption plateau pressure was increased and the hydrogen storage capacity was enhanced with the increase of Mn content The absorption/desorption plateau pressure of the alloys was linearly changed with the Mn content x and the lattice parameter a while the hydrogen storage capacity was linearly increased with the increase of c/a ratio It was also found that the slope factor S-f was closely correlated with the lattice strain of the alloys (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved