Carbon dioxide absorbent, the carbon dioxide separation method, and carbon dioxide gas separating apparatus using the same

A component material X is at least one of Sr and Ba, and Ti, the molar ratio (X / Ti): as a main component a complex oxide in a proportion of 1.8 to 2.2. Also, the X and Ti, the molar ratio (X / Ti): material having a perovskite structure in a proportion of 0.9 to 1.1, or a green sheet comprising them, green sheet wastes, green sheet laminate wastes, green at least one sheet precursors calcined at least one presence of strontium carbonate and barium carbonate. Using carbon dioxide absorbent 3 of the present