Impact of NiO pre-doping on CoO incorporation into BaZr0.4Ce0.4Y0.1Yb0.1O3−δ and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ electrolytes

Barium zirconate–cerate electrolytes BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3−δ (BZCYYb4411) and BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb1711) are synthesized via a Pechini method at 1200 °C for 5 h to explore a NiO pre-doping strategy to control CoO incorporation in proton-conducting electrolytes for proton ceramic fuel cells. BZCYYb4411 and BZCYYb1711 adopt cubic perovskite and monoclinic structures, respectively. The chemical compatibility and extent of reaction of these materials with NiO and CoO are evaluated. Approximately 2 mol% of Ni 2+ is incorporated into the perovskite lattices of both BZCYYb4411 and BZCYYb1711 upon their reaction with NiO, which reduces the lattice parameter of BZCYYb4411 and induces a monoclinic to orthorhombic phase transition in BZCYYb1711. Moreover, the reaction with CoO reduces the lattice parameters of both BZCYYb4411 and BZCYYb1711 via the incorporation of Co 2+ /Co 3+ . The introduction of CoO into samples pre-doped with Ni 2+ limits Co 2+ /Co 3+ incorporation to approximately 3 mol%; thus, Ni 2+ pre-doping suppresses Co 2+ /Co 3+ incorporation into BZCYYb4411 and BZCYYb1711.