Oxygen Permeability, Stability and Electrochemical Behavior of % Mathtype!Translator!2!1!Ams Latex.tdl!Tex -- Ams-Latex! % Mathtype!Mtef!2!1!+- % Feaaeaart1Ev0Aaatcvaufebsjuyzl2Yd9Gzlbvynv2Caerbbjxahx % Garmwu51Myvxgatuudjxwak1Uy0Hwmaehbfv3Yslgzg0Uy0Hgip5Wz % Aebbnrfifhhdyfgasaach8Qrps0Lbbf9Q8Wrffeuy-Hhbbf9V8Qqaq % Fr0Xc9Pk0Xbba9Q8Wqffea0-Yr0Ryxir-Jbba9Q8Aq0-Yq-He9Q8Qq % Q8Frfve9Fve9Ff0Dmeaabaqacigacagaaeqabawaaewaeaaakeaaci % Ggqbgaaiocamaabaaaleaacaaiyaaabeaakiaab6Eacaqgpbgaae4T % Amaabaaaleaacaai0Agaey4Kasiaeqitdqgabeaaaaa!404E! $$ \Pr _{2} {\Text{Nio}}_{{4 + \Delta }} $$ -Based Materials