Rational design of mixed ionic and electronic conducting perovskite oxides for solid oxide fuel cell anode materials: A case study for doped SrTiO_3

摘要

The effect of p- and n-type dopants on ionic and electronic conductivity of SrTiO_3 based perovskites were investigated both computationally and experimentally. Specifically, we performed density functional theory (DFT) calculations of Na- and La-doped SrTiO_3 and Na- and Nb-doped SrTiO_3 systems. Constrained ab initio thermodynamic calculations were used to evaluate the phase stability and reducibility of doped SrTiO_3 under both oxidizing and reducing synthesis conditions, as well as under anodic solid oxide fuel cell (SOFC) conditions. The density of states (DOS) of these materials was analyzed to study the effects of p- and n-doping on the electronic conductivity. Furthermore, Na- and La-doped SrTiO_3 and Na- and Nb-doped SrTiO_3 samples were experimentally prepared and the conductivity was measured to confirm our computational predictions. The experimental observations are in very good agreement with the theoretical predictions that doping n-doped SrTiO_3 with small amounts of p-type dopants promotes both the ionic and electronic conductivity of the material. This doping strategy is valid independent of p- and n-doping site and permits the synthesis of perovskite based mixed ionic/electronic conductors.