Tailoring phase stability and electrical conductivity of Sr0.02La0.98Nb1-xTaxO4 for intermediate temperature fuel cell proton conducting electrolytes

► Sr0.02La0.98Nb1-xTaxO4 with x = 0.1, 0.2, 0.4 was synthesized by solid state reaction. ► Increasing tantalum content led to a decreased in the phase transition temperature. ► Increasing the tantalum content decreased the total conductivity. ► The best compromise was found for the Sr0.02La0.98Nb0.98Ta0.02O4 composition.