Ni-ferrite is a promising reactive ceramics of the ferrite for the solar hydrogen production by a two-step water splitting process using concentrated solar energy. However, it should be pretreated before -generation reaction by grinding the Ni-ferrite sintered after the -releasing reaction to make a fine powder. If the Ni-ferrite and yttria stabilized zirconia (YSZ) form a solid solution between these oxides ( solid ), it is expected that the two-step water splitting process with the Ni-ferrite system can proceed without treatment of the reduced product because of the high thermal stability of the solid solution. The solid solution was prepared by calcination of the mixture of the YSZ balls and powder at for , and its reactivity and thermal stability were examined for the two-step water splitting process. During the ten times repetition of the two-step water splitting reaction ( for -releasing, and for -generation) with the solid solution using infrared imaging furnace, the reactivity for -releasing and -generation was kept constant. The molar ratio of the released gas volume (the average gas, ) and the generated gas volume (the average gas, ) was nearly 1:2, indicating that the water decomposition process via two steps proceeds. The X-ray diffractometry (XRD) measurement showed that the YSZ(Ni,Fe) keeps the YSZ phase structure during the ten times repetition of the two-step water splitting process. The successive gas production by the two-step water splitting process was performed (ten times repetition of the two-step water splitting process). From comparative study on the reactivity and the thermal stability for the two-step water splitting reaction among the solid solution, and , it is concluded that the solid solution is superior to the others.