We investigated phase transition of ilmenite-type AgSbO3 to pyrochlore by post-heat treatment and the synergy effect of the mixed phases of AgSbO3 on the photocatalytic activities to enhance the activities. The AgSbO3 with an ilmenite structure was prepared by a cation-exchange method. Phase transition from the ilmenite to pyrochlore occurred by proper control of post-heat treatment. The sample that was obtained by post-heat treatment of ilmenite-type AgSbO3 at 660 degrees C for 3h consisted of both of the ilmenite and pyrochlore phases, and the sample at 685 degrees C for 4 h mainly consisted of the pyrochlore phase. Together with an increase in the ratio of the pyrochlore phase, the optical absorption spectra blue-shifted. The band gaps of single phases of the ilmenite and the pyrochlore were 2.4 and 2.6 eV, respectively. The AgSbO3 sample obtained by post-heat treatment at 660 degrees C for 3 h showed about eight times and twice higher photocatalytic activity under visible light irradiation than a standard TiO2 photocatalyst (Degussa P25) and single phase of the ilmenite-type sample, respectively, because of the synergy effect. (c) 2010 Elsevier B.V. All rights reserved.