Strontium zirconate-based materials have been studied as potential high-temperature protonic conductors. Yttrium for zirconium substitution, and lanthanum for strontium substitution were selected to demonstrate that changes in composition can be used as a tool to design the properties. At temperatures below about 900 ° C, both yttrium-doped and undoped strontium zirconate are mostly protonic conductors at oxygen partial pressures below about 1 Pa, and mixed ionic and p-type conductors at higher pressures. The main ionic contribution changes from mostly protonic to oxygen-ion conduction with increasing temperature, which may affect the performance of electrochemical devices. Yttrium for zirconium substitution enhances both the electronic and ionic conductivities. Lanthanum for strontium substitution suppresses protonic conduction and gives rise to mixed oxygen-ion and n-type conduction in reducing conditions.