In the O-2-releasing step of water splitting system, MnFe2O4 was completely regenerated from Na(Mn1/3Fe2/3)O2+delta by enhancement of O-2-releasing step with Fe2O3 at 1273 K. Thermodynamic data for the enhancement of the O-2-releasing step with alpha -Fe2O3 in the water splitting with the MnFe2O3-Na2CO3 system are experimentally confirmed. The amount of released oxygen attained to the theoretical value at around 1273 K (Po-2 = 10(-6)) and about 1240 K (Po-2 = 10(-7)). At higher temperature above 1273 K (Po-2 = 10(-6)) and 1240 K (Po-2 = 10(-7)), the released oxygen amount increased. In the three-step water splitting system with MnFe2O3-Na2CO3-Fe2O3, we proposed that there are some advantages required for application to the solar thermochemical process. (C) 2001 Elsevier Science Ltd. All rights reserved.