電気化学的手法によるCa_<1-x>Sr_xFeO_<3-z>ペロブスカイト酸化物への酸素ドープ

概要

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Oxygen doped Ca_<1-x>Sr_xFeO_<3-x>(0〓x〓1.0, z=0.25-0) perovskite type oxides were prepared by treating grossly oxygen-deficient samples using an electrochemical oxidation technique at room temperature. Although the oxygen-deficient starting samples in the Ca-rich region (CaFeO_<2.5> and Ca_<0.8>Sr_<0.2>FeO_<2.5>) had high resistivity, it was possible to dope oxygen when a high current and a high electrode potential were applied. However, there is no reproducibility in preparing them. Ca_<1-x>Sr_xFeO_<3-z> in the Ca rich region (x= 0.4-0.0) showed a gradual metal-insulator (MI) transition due to the charge disproportionation of Fe^<4+> (2Fe^<4+> 〓Fe^<3+> + Fe^<5+>) below room temperature. For the oxygen doping of the perovskite oxides, applying only a few hundred mV of electrode potential creates the same effect as a long annealing at high oxygen pressure of more than a few hundred MPa. Although the lack of stability after electrolysis is a weak point, the electrochemical reaction is a simple and easy way to creates the oxygen doped state of the perovskite oxides.
社団法人日本セラミックス協会の論文
1998-08-01