In view of the blanket design of a futuristic deuterium-tritium fusion reactor, a time-dependent study of 14-MeV neutrons has been carried out in bare lithium and Li2O blanket assemblies with different concentrations of 6Li nuclei. For assemblies of different sizes, time-dependent total neutron fluxes, a tritium production rate (TPR), and a tritium breeding ratio (TBR) up to 40% concentration of 6Li (natural concentration being 7.42 at.%) have been reported. A multigroup diffusion equation and eigenfunction expansion method has been used. This study shows that for any concentration of 6Li, the values of TPR as well as TBR are higher for a Li2O assembly than those obtained for all corresponding (of same size) assemblies of lithium. However, for a given assembly of lithium or Li2O, the TBR values do not show any observable change with 6Li concentration beyond ~40%. Further, for any concentration, the values of TPR and TBR decrease substantially in both types of systems as the side of the cubic assembly is reduced from 1 to 0.5 m.